Revised.
This commit is contained in:
Werner Lemberg
parent
9348b9fc50
commit
904c1e15bf
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@ -56,6 +56,8 @@
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</table>
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</center>
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<p><hr></p>
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<table width="100%">
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<tr bgcolor="#CCCCFF"
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valign=center><td>
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@ -166,6 +168,8 @@
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they are usually expressed in pixels then.</p>
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<p><hr></p>
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<center>
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<table width="100%"
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border=0
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@ -1,12 +1,13 @@
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<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
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<!doctype html public "-//w3c//dtd html 4.0 transitional//en"
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"http://www.w3.org/TR/REC-html40/loose.dtd">
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<meta name="Author" content="blob">
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<meta name="GENERATOR" content="Mozilla/4.5 [fr] (Win98; I) [Netscape]">
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<title>FreeType Glyph Conventions</title>
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<meta http-equiv="Content-Type"
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content="text/html; charset=iso-8859-1">
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<meta name="Author"
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content="David Turner">
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<title>FreeType Glyph Conventions</title>
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</head>
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<body>
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<body text="#000000"
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bgcolor="#FFFFFF"
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@ -14,354 +15,381 @@
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vlink="#51188E"
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alink="#FF0000">
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<center><h1>
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FreeType Glyph Conventions
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</h1></center>
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<h1 align=center>
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FreeType Glyph Conventions
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</h1>
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<center><h2>
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version 2.1
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</h2></center>
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<h2 align=center>
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Version 2.1
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</h2>
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<center><h3>
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Copyright 1998-2000 David Turner (<a href="mailto:david@freetype.org">david@freetype.org</a>)<br>
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Copyright 2000 The FreeType Development Team (<a href="devel@freetype.org">devel@freetype.org</a>)
|
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</h3></center>
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<center><table width=650><tr><td>
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<center><table width="100%" border=0 cellpadding=5><tr bgcolor="#CCFFCC" valign=center>
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||||
<td align=center width="30%">
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||||
<a href="glyphs-1.html">Previous</a>
|
||||
</td>
|
||||
<td align=center width="30%">
|
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<a href="index.html">Contents</a>
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||||
</td>
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||||
<td align=center width="30%">
|
||||
<a href="glyphs-3.html">Next</a>
|
||||
</td>
|
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</tr></table></center>
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<table width="100%" cellpadding=4><tr bgcolor="#CCCCFF" valign=center><td><h2>
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II. Glyph Outlines
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</h2></td></tr></table>
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<p>This section describes the way scalable representation of glyph images,
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called outlines, are used by FreeType as well as client applications.</p>
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<h3><a name="section-1">
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1. Pixels, Points and Device Resolutions :
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</h3><blockquote>
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<p>Though it is a very common assumption when dealing with computer
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graphics programs, the physical dimensions of a given pixel (be it for
|
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screens or printers) are not squared. Often, the output device, be it a
|
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screen or printer exhibits varying resolutions in the horizontal and vertical
|
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directions, and this must be taken care of when rendering text.
|
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</p>
|
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|
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<p>It is thus common to define a device's characteristics through two numbers
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expressed in <b>dpi</b> (dots per inch). For example, a printer with a
|
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resolution of 300x600 dpi has 300 pixels per inch in the horizontal
|
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direction, and 600 in the vertical one. The resolution of a typical computer
|
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monitor varies with its size (a 15" and 17" monitors don't have the same
|
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pixel sizes at 640x480), and of course the graphics mode resolution.
|
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</p>
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|
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<p>As a consequence, the size of text is usually given in <b>points</b>,
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rather than device-specific pixels. Points are a simple <i>physical</i>
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unit, where 1 point = 1/72th of an inch, in digital typography. As an
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example, most roman books are printed with a body text which size is
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chosen between 10 and 14 points.</p>
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<p>It is thus possible to compute the size of text in pixels from the size
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in points through the following computation :</p>
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<h3 align=center>
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Copyright 1998-2000 David Turner (<a
|
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href="mailto:david@freetype.org">david@freetype.org</a>)<br>
|
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Copyright 2000 The FreeType Development Team (<a
|
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href="mailto:devel@freetype.org">devel@freetype.org</a>)
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</h3>
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<center>
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<p><tt>pixel_size = point_size * resolution / 72</tt></center>
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<table width="65%">
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<tr><td>
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<p>Where resolution is expressed in <em>dpi</em>. Note that because the
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horizontal and vertical resolutions may differ, a single point size
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usually defines different text width and height in pixels.</p>
|
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<center>
|
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<table width="100%"
|
||||
border=0
|
||||
cellpadding=5>
|
||||
<tr bgcolor="#CCFFCC"
|
||||
valign=center>
|
||||
<td align=center
|
||||
width="30%">
|
||||
<a href="glyphs-1.html">Previous</a>
|
||||
</td>
|
||||
<td align=center
|
||||
width="30%">
|
||||
<a href="index.html">Contents</a>
|
||||
</td>
|
||||
<td align=center
|
||||
width="30%">
|
||||
<a href="glyphs-3.html">Next</a>
|
||||
</td>
|
||||
</tr>
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||||
</table>
|
||||
</center>
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<p><b>IMPORTANT NOTE:</b>
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<br><i>Unlike what is often thought, the "size of text in pixels" is not
|
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directly related to the real dimensions of characters when they're displayed
|
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or printed. The relationship between these two concepts is a bit more complex
|
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and relate to some design choice made by the font designer. This is described
|
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in more details the next sub-section (see the explanations on the EM square).
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</i></p>
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<p><hr></p>
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<table width="100%">
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<tr bgcolor="#CCCCFF"
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valign=center><td>
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<h2>
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II. Glyph Outlines
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</h2>
|
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</td></tr>
|
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</table>
|
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|
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<p>This section describes the way scalable representation of glyph images,
|
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called outlines, are used by FreeType as well as client applications.</p>
|
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|
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<a name="section-1">
|
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<h3>
|
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1. Pixels, points and device resolutions
|
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</h3>
|
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|
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<p>Though it is a very common assumption when dealing with computer
|
||||
graphics programs, the physical dimensions of a given pixel (be it for
|
||||
screens or printers) are not squared. Often, the output device, be it a
|
||||
screen or printer, exhibits varying resolutions in both horizontal and
|
||||
vertical direction, and this must be taken care of when rendering
|
||||
text.</p>
|
||||
|
||||
<p>It is thus common to define a device's characteristics through two
|
||||
numbers expressed in <em>dpi</em> (dots per inch). For example, a
|
||||
printer with a resolution of 300x600 dpi has 300 pixels per
|
||||
inch in the horizontal direction, and 600 in the vertical one. The
|
||||
resolution of a typical computer monitor varies with its size
|
||||
(15" and 17" monitors don't have the same pixel sizes at
|
||||
640x480), and of course the graphics mode resolution.</p>
|
||||
|
||||
<p>As a consequence, the size of text is usually given in
|
||||
<em>points</em>, rather than device-specific pixels. Points are a
|
||||
simple <em>physical</em> unit, where 1 point = 1/72th of
|
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an inch, in digital typography. As an example, most Roman books are
|
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printed with a body text which size is chosen between 10 and
|
||||
14 points.</p>
|
||||
|
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<p>It is thus possible to compute the size of text in pixels from the
|
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size in points with the following formula:</p>
|
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|
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<center>
|
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<tt>pixel_size = point_size * resolution / 72</tt>
|
||||
</center>
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|
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<p>The resolution is expressed in <em>dpi</em>. Since horizontal and
|
||||
vertical resolutions may differ, a single point size usually defines a
|
||||
different text width and height in pixels.</p>
|
||||
|
||||
<p><em>Unlike what is often thought, the "size of text in pixels" is not
|
||||
directly related to the real dimensions of characters when they are
|
||||
displayed or printed. The relationship between these two concepts is a
|
||||
bit more complex and relate to some design choices made by the font
|
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designer. This is described in more detail in the next sub-section (see
|
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the explanations on the EM square).</em></p>
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|
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|
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<a name="section-2">
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<h3>
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2. Vectorial representation
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</h3>
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</blockquote><h3><a name="section-2">
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2. Vectorial representation :
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</h3><blockquote>
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<p>The source format of outlines is a collection of closed paths called
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<em>contours</em>. Each contour delimits an outer or inner
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<em>region</em> of the glyph, and can be made of either <em>line
|
||||
segments</em> or <em>Bézier arcs</em>.</p>
|
||||
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<p>The arcs are defined through <em>control points</em>, and can be
|
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either second-order (these are <em>conic</em> Béziers) or
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third-order (<em>cubic</em> Béziers) polynomials, depending on
|
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the font format. Note that conic Béziers are usually called
|
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<em>quadratic</em> Béziers in the literature. Hence, each point
|
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of the outline has an associated flag indicating its type (normal or
|
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control point). And scaling the points will scale the whole
|
||||
outline.</p>
|
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|
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<p>Each glyph's original outline points are located on a grid of
|
||||
indivisible units. The points are usually stored in a font file as
|
||||
16-bit integer grid coordinates, with the grid origin's being at (0,0);
|
||||
they thus range from -16384 to 16383. (Even though point
|
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coordinates can be floats in other formats such as Type 1, we will
|
||||
restrict our analysis to integer values for simplicity).</p>
|
||||
|
||||
<p><em>The grid is always oriented like the traditional mathematical
|
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two-dimensional plane, i.e., the <i>X</i> axis from the left to the
|
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right, and the <i>Y</i> axis from bottom to top.</em></p>
|
||||
|
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<p>In creating the glyph outlines, a type designer uses an imaginary
|
||||
square called the <em>EM square</em>. Typically, the EM square can be
|
||||
thought of as a tablet on which the character are drawn. The square's
|
||||
size, i.e., the number of grid units on its sides, is very important for
|
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two reasons:</p>
|
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|
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<ul>
|
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<li>
|
||||
<p>It is the reference used to scale the outlines to a given text
|
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dimension. For example, a size of 12pt at 300x300 dpi
|
||||
corresponds to 12*300/72 = 50 pixels. This is the
|
||||
size the EM square would appear on the output device if it was
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||||
rendered directly. In other words, scaling from grid units to
|
||||
pixels uses the formula:</p>
|
||||
|
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<p><center>
|
||||
<tt>pixel_size = point_size * resolution / 72</tt><br>
|
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<tt>pixel_coord = grid_coord * pixel_size / EM_size</tt>
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||||
</center></p>
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||||
</li>
|
||||
<li>
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||||
<p>The greater the EM size is, the larger resolution the designer
|
||||
can use when digitizing outlines. For example, in the extreme
|
||||
example of an EM size of 4 units, there are only 25 point
|
||||
positions available within the EM square which is clearly not
|
||||
enough. Typical TrueType fonts use an EM size of 2048 units;
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Type 1 PostScript fonts have a fixed EM size of 1000 grid
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units but point coordinates can be expressed as floating values.</p>
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</li>
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</ul>
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<p>Note that glyphs can freely extend beyond the EM square if the font
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designer wants so. The EM is used as a convenience, and is a valuable
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convenience from traditional typography.</p>
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<p>Grid units are very often called <em>font units</em> or <em>EM
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units</em>.</p>
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<p><em>As said before, <tt>pixel_size</tt> computed in the above formula
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does not relate directly to the size of characters on the screen. It
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simply is the size of the EM square if it was to be displayed. Each
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font designer is free to place its glyphs as it pleases him within the
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square. This explains why the letters of the following text have not
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the same height, even though they are displayed at the same point size
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with distinct fonts:</em>
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<p><center>
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<img src="body_comparison.png"
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height=40 width=580
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alt="Comparison of font heights">
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</center></p>
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<p>As one can see, the glyphs of the Courier family are smaller than
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those of Times New Roman, which themselves are slightly smaller than
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those of Arial, even though everything is displayed or printed at a size
|
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of 16 points. This only reflects design choices.</p>
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<a name="section-3">
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<h3>
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3. Hinting and Bitmap rendering
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</h3>
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<p>The source format of outlines is a collection of closed paths
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called <b>contours</b>. Each contour delimits an outer or inner <i>region</i>
|
||||
of the glyph, and can be made of either <b>line segments</b> or <b>bezier
|
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arcs</b>.</p>
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<p>The outline as stored in a font file is called the "master" outline,
|
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as its points coordinates are expressed in font units. Before it can be
|
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converted into a bitmap, it must be scaled to a given size/resolution.
|
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This is done through a very simple transformation, but always creates
|
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undesirable artifacts, e.g. stems of different widths or heights in
|
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letters like "E" or "H".</p>
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<p>The arcs are defined through <b>control points</b>, and can be either
|
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second-order (these are "conic" beziers) or third-order ("cubic" beziers) polynomials, depending on
|
||||
the font format. Note that conic beziers are usually called "quadratic"
|
||||
beziers in the literature. Hence, each point of the outline has an
|
||||
associated <b>flag</b> indicating its type (normal or control point).
|
||||
And scaling the points will scale the whole outline.
|
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</p>
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<p>As a consequence, proper glyph rendering needs the scaled points to
|
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be aligned along the target device pixel grid, through an operation
|
||||
called <em>grid-fitting</em>, and often <em>hinting</em>. One of its
|
||||
main purposes is to ensure that important widths and heights are
|
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respected throughout the whole font (for example, it is very often
|
||||
desirable that the "I" and the "T" have their central vertical line of
|
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the same pixel width), as well as to manage features like stems and
|
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overshoots, which can cause problems at small pixel sizes.</p>
|
||||
|
||||
<p>Each glyph's original outline points are located on a grid of indivisible
|
||||
units. The points are usually stored in a font file as 16-bit integer grid
|
||||
coordinates, with the grid origin's being at (0,0); they thus range from
|
||||
-16384 to 16383. (even though point coordinates can be floats in other
|
||||
formats such as Type 1, we'll restrict our analysis to integer ones, driven
|
||||
by the need for simplicity..).
|
||||
</p>
|
||||
<p>There are several ways to perform grid-fitting properly; most
|
||||
scalable formats associate some control data or programs with each glyph
|
||||
outline. Here is an overview:</p>
|
||||
|
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<p><b>IMPORTANT NOTE:</b>
|
||||
<br><i>The grid is always oriented like the traditional mathematical 2D
|
||||
plane, i.e. the X axis from the left to the right, and the Y axis from
|
||||
bottom to top.</i></p>
|
||||
<ul>
|
||||
<li>
|
||||
<p><em>explicit grid-fitting</em></p>
|
||||
|
||||
<p>In creating the glyph outlines, a type designer uses an imaginary square
|
||||
called the "EM square". Typically, the EM square can be thought of as a
|
||||
tablet on which the character are drawn. The square's size, i.e., the number
|
||||
of grid units on its sides, is very important for two reasons:</p>
|
||||
<p>The TrueType format defines a stack-based virtual machine, for
|
||||
which programs can be written with the help of more than
|
||||
200 opcodes (most of these relating to geometrical operations).
|
||||
Each glyph is thus made of both an outline and a control program to
|
||||
perform the actual grid-fitting in the way defined by the font
|
||||
designer.</p>
|
||||
</li>
|
||||
<li>
|
||||
<p><em>implicit grid-fitting (also called hinting)</em></p>
|
||||
|
||||
<ul>
|
||||
<li><p>
|
||||
it is the reference used to scale the outlines to a given text dimension.
|
||||
For example, a size of 12pt at 300x300 dpi corresponds to 12*300/72 = 50
|
||||
pixels. This is the size the EM square would appear on the output device
|
||||
if it was rendered directly. In other words, scaling from grid units to
|
||||
pixels uses the formula:</p>
|
||||
<p>The Type 1 format takes a much simpler approach: Each glyph
|
||||
is made of an outline as well as several pieces called
|
||||
<em>hints</em> which are used to describe some important features of
|
||||
the glyph, like the presence of stems, some width regularities, and
|
||||
the like. There aren't a lot of hint types, and it is up to the
|
||||
final renderer to interpret the hints in order to produce a fitted
|
||||
outline.</p>
|
||||
</li>
|
||||
<li>
|
||||
<p><em>automatic grid-fitting</em></p>
|
||||
|
||||
<p><center><tt>pixel_size = point_size * resolution / 72</tt>
|
||||
<br><tt>pixel_coordinate = grid_coordinate * pixel_size / EM_size</tt>
|
||||
</center></p>
|
||||
<p>Some formats simply include no control information with each
|
||||
glyph outline, apart metrics like the advance width and height. It
|
||||
is then up to the renderer to "guess" the more interesting features
|
||||
of the outline in order to perform some decent grid-fitting.</p>
|
||||
</li>
|
||||
</ul>
|
||||
|
||||
<p>The following table summarises the pros and cons of each scheme.</p>
|
||||
|
||||
<li><p>
|
||||
the greater the EM size is, the larger resolution the designer can use
|
||||
when digitizing outlines. For example, in the extreme example of an EM
|
||||
size of 4 units, there are only 25 point positions available within the
|
||||
EM square which is clearly not enough. Typical TrueType fonts use an EM
|
||||
size of 2048 units (note: with Type 1 PostScript fonts, the EM size is
|
||||
fixed to 1000 grid units. However, point coordinates can be expressed in
|
||||
floating values).
|
||||
</p></li>
|
||||
</ul>
|
||||
<center>
|
||||
<table width="90%"
|
||||
bgcolor="#CCCCCC"
|
||||
cellpadding=5>
|
||||
<tr bgcolor="#999999">
|
||||
<td>
|
||||
<center>
|
||||
<b>grid-fitting scheme</b>
|
||||
</center>
|
||||
</td>
|
||||
<td>
|
||||
<center>
|
||||
<b>advantages</b>
|
||||
</center>
|
||||
</td>
|
||||
<td>
|
||||
<center>
|
||||
<b>disadvantages</b>
|
||||
</center>
|
||||
</td>
|
||||
</tr>
|
||||
|
||||
<p>Note that glyphs can freely extend beyond the EM square if the font
|
||||
designer wants so. The EM is used as a convenience, and is a valuable
|
||||
convenience from traditional typography.</p>
|
||||
<tr>
|
||||
<td valign=top>
|
||||
<center>
|
||||
<b>explicit</b>
|
||||
</center>
|
||||
</td>
|
||||
|
||||
<center>
|
||||
<p><b>Note : Grid units are very often called "font units" or "EM units".</b></center>
|
||||
<td valign=top>
|
||||
<p><b>Quality.</b> Excellent results at small sizes are possible.
|
||||
This is very important for screen display.</p>
|
||||
|
||||
<p><b>NOTE:</b>
|
||||
<br><i>As said before, the pixel_size computed in the above formula
|
||||
does not relate directly to the size of characters on the screen. It simply
|
||||
is the size of the EM square if it was to be displayed directly. Each font
|
||||
designer is free to place its glyphs as it pleases him within the square.
|
||||
This explains why the letters of the following text have not the same height,
|
||||
even though they're displayed at the same point size with distinct fonts
|
||||
:</i>
|
||||
<center>
|
||||
<p><img SRC="body_comparison.png" height=40 width=580></center>
|
||||
<p><b>Consistency.</b> All renderers produce the same glyph
|
||||
bitmaps.</p>
|
||||
</td>
|
||||
|
||||
<p>As one can see, the glyphs of the Courier family are smaller than those
|
||||
of Times New Roman, which themselves are slightly smaller than those of
|
||||
Arial, even though everything is displayed or printed at a size of
|
||||
16 points. This only reflect design choices.
|
||||
</p>
|
||||
<td valign=top>
|
||||
<p><b>Speed.</b> Intepreting bytecode can be slow if the glyph
|
||||
programs are complex.</p>
|
||||
|
||||
<p><b>Size.</b> Glyph programs can be long.</p>
|
||||
|
||||
<p><b>Technicity.</b>
|
||||
It is extremely difficult to write good hinting
|
||||
programs. Very few tools available.</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td valign=top>
|
||||
<center>
|
||||
<b>implicit</b>
|
||||
</center>
|
||||
</td>
|
||||
|
||||
</blockquote><h3><a name="section-3">
|
||||
3. Hinting and Bitmap rendering
|
||||
</h3><blockquote>
|
||||
<td valign=top>
|
||||
<p><b>Size.</b> Hints are usually much smaller than explicit glyph
|
||||
programs.</p>
|
||||
|
||||
<p>The outline as stored in a font file is called the "master"
|
||||
outline, as its points coordinates are expressed in font units. Before
|
||||
it can be converted into a bitmap, it must be scaled to a given
|
||||
size/resolution. This is done through a very simple transform, but always
|
||||
creates undesirable artifacts, e.g. stems of different widths or heights
|
||||
in letters like "E" or "H".
|
||||
</p>
|
||||
<p><b>Speed.</b>
|
||||
Grid-fitting is usually a fast process.</p>
|
||||
</td>
|
||||
|
||||
<p>As a consequence, proper glyph rendering needs the scaled points to
|
||||
be aligned along the target device pixel grid, through an operation called
|
||||
"grid-fitting", and often "hinting". One of its main purpose is to ensure
|
||||
that important widths and heights are respected throughout the whole font
|
||||
(for example, it is very often desirable that the "I" and the "T" have
|
||||
their central vertical line of the same pixel width), as well as manage
|
||||
features like stems and overshoots, which can cause problems at small pixel
|
||||
sizes.
|
||||
</p>
|
||||
<td valign=top>
|
||||
<p><b>Quality.</b> Often questionable at small sizes. Better with
|
||||
anti-aliasing though.</p>
|
||||
|
||||
<p>There are several ways to perform grid-fitting properly, for example
|
||||
most scalable formats associate some control data or programs with each
|
||||
glyph outline. Here is an overview :</p>
|
||||
<p><b>Inconsistency.</b> Results can vary between different
|
||||
renderers, or even distinct versions of the same engine.</p>
|
||||
</td>
|
||||
</tr>
|
||||
|
||||
<blockquote>
|
||||
<blockquote><b>explicit grid-fitting :</b>
|
||||
<blockquote>The TrueType format defines a stack-based virtual machine,
|
||||
for which programs can be written with the help of more than 200 opcodes
|
||||
(most of these relating to geometrical operations). Each glyph is thus
|
||||
made of both an outline and a control program, its purpose being to perform
|
||||
the actual grid-fitting in the way defined by the font designer.</blockquote>
|
||||
<tr>
|
||||
<td valign=top>
|
||||
<center>
|
||||
<b>automatic</b>
|
||||
</center>
|
||||
</td>
|
||||
|
||||
<p><br><b>implicit grid-fitting (also called hinting) :</b>
|
||||
<blockquote>The Type 1 format takes a much simpler approach : each glyph
|
||||
is made of an outline as well as several pieces called "hints" which are
|
||||
used to describe some important features of the glyph, like the presence
|
||||
of stems, some width regularities, and the like. There aren't a lot of
|
||||
hint types, and it's up to the final renderer to interpret the hints in
|
||||
order to produce a fitted outline.</blockquote>
|
||||
<td valign=top>
|
||||
<p><b>Size.</b> No need for control information, resulting in
|
||||
smaller font files.</p>
|
||||
|
||||
<p><br><b>automatic grid-fitting :</b>
|
||||
<blockquote>Some formats simply include no control information with each
|
||||
glyph outline, apart metrics like the advance width and height. It's then
|
||||
up to the renderer to "guess" the more interesting features of the outline
|
||||
in order to perform some decent grid-fitting.</blockquote>
|
||||
</blockquote>
|
||||
</blockquote>
|
||||
<p><b>Speed.</b> Depends on the grid-fitting algorithm. Usually
|
||||
faster than explicit grid-fitting.</p>
|
||||
</td>
|
||||
|
||||
<center>
|
||||
<p><br>The following table summarises the pros and cons of each scheme
|
||||
:</center>
|
||||
</blockquote>
|
||||
<td valign=top>
|
||||
<p><b>Quality.</b> Often questionable at small sizes. Better with
|
||||
anti-aliasing though.</p>
|
||||
|
||||
<center><table BORDER=0 WIDTH="80%" BGCOLOR="#CCCCCC" >
|
||||
<tr BGCOLOR="#999999">
|
||||
<td>
|
||||
<blockquote>
|
||||
<center><b><font color="#000000">Grid-fitting scheme</font></b></center>
|
||||
</blockquote>
|
||||
</td>
|
||||
<p><b>Speed.</b> Depends on the grid-fitting algorithm.</p>
|
||||
|
||||
<td>
|
||||
<blockquote>
|
||||
<center><b><font color="#000000">Pros</font></b></center>
|
||||
</blockquote>
|
||||
</td>
|
||||
<p><b>Inconsistency.</b> Results can vary between different
|
||||
renderers, or even distinct versions of the same engine.</p>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
</center>
|
||||
|
||||
<td>
|
||||
<blockquote>
|
||||
<center><b><font color="#000000">Cons</font></b></center>
|
||||
</blockquote>
|
||||
</td>
|
||||
</tr>
|
||||
<p><hr></p>
|
||||
|
||||
<tr>
|
||||
<td>
|
||||
<blockquote>
|
||||
<center><b><font color="#000000">Explicit</font></b></center>
|
||||
</blockquote>
|
||||
</td>
|
||||
<center>
|
||||
<table width="100%"
|
||||
border=0
|
||||
cellpadding=5>
|
||||
<tr bgcolor="#CCFFCC"
|
||||
valign=center>
|
||||
<td align=center
|
||||
width="30%">
|
||||
<a href="glyphs-1.html">Previous</a>
|
||||
</td>
|
||||
<td align=center
|
||||
width="30%">
|
||||
<a href="index.html">Contents</a>
|
||||
</td>
|
||||
<td align=center
|
||||
width="30%">
|
||||
<a href="glyphs-3.html">Next</a>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
</center>
|
||||
|
||||
<td>
|
||||
<blockquote>
|
||||
<center><b><font color="#000000">Quality</font></b>
|
||||
<br><font color="#000000">excellence at small sizes is possible. This is
|
||||
very important for screen display.</font>
|
||||
<p><b><font color="#000000">Consistency</font></b>
|
||||
<br><font color="#000000">all renderers produce the same glyph bitmaps.</font></center>
|
||||
</blockquote>
|
||||
</td>
|
||||
</td></tr>
|
||||
</table>
|
||||
</center>
|
||||
|
||||
<td>
|
||||
<blockquote>
|
||||
<center><b><font color="#000000">Speed</font></b>
|
||||
<br><font color="#000000">intepreting bytecode can be slow if the glyph
|
||||
programs are complex.</font>
|
||||
<p><b><font color="#000000">Size</font></b>
|
||||
<br><font color="#000000">glyph programs can be long</font>
|
||||
<p><b><font color="#000000">Technicity</font></b>
|
||||
<br><font color="#000000">it is extremely difficult to write good hinting
|
||||
programs. Very few tools available.</font></center>
|
||||
</blockquote>
|
||||
</td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td>
|
||||
<blockquote>
|
||||
<center><b><font color="#000000">Implicit</font></b></center>
|
||||
</blockquote>
|
||||
</td>
|
||||
|
||||
<td>
|
||||
<blockquote>
|
||||
<center><b><font color="#000000">Size</font></b>
|
||||
<br><font color="#000000">hints are usually much smaller than explicit
|
||||
glyph programs.</font>
|
||||
<p><b><font color="#000000">Speed</font></b>
|
||||
<br><font color="#000000">grid-fitting is usually a fast process</font></center>
|
||||
</blockquote>
|
||||
</td>
|
||||
|
||||
<td>
|
||||
<blockquote>
|
||||
<center><b><font color="#000000">Quality</font></b>
|
||||
<br><font color="#000000">often questionable at small sizes. Better with
|
||||
anti-aliasing though.</font>
|
||||
<p><b><font color="#000000">Inconsistency</font></b>
|
||||
<br><font color="#000000">results can vary between different renderers,
|
||||
or even distinct versions of the same engine.</font></center>
|
||||
</blockquote>
|
||||
</td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td>
|
||||
<blockquote>
|
||||
<center><b><font color="#000000">Automatic</font></b></center>
|
||||
</blockquote>
|
||||
</td>
|
||||
|
||||
<td>
|
||||
<blockquote>
|
||||
<center><b><font color="#000000">Size</font></b>
|
||||
<br><font color="#000000">no need for control information, resulting in
|
||||
smaller font files.</font>
|
||||
<p><b><font color="#000000">Speed</font></b>
|
||||
<br><font color="#000000">depends on the grid-fitting algo.Usually faster
|
||||
than explicit grid-fitting.</font></center>
|
||||
</blockquote>
|
||||
</td>
|
||||
|
||||
<td>
|
||||
<blockquote>
|
||||
<center><b><font color="#000000">Quality</font></b>
|
||||
<br><font color="#000000">often questionable at small sizes. Better with
|
||||
anti-aliasing though</font>
|
||||
<p><b><font color="#000000">Speed</font></b>
|
||||
<br><font color="#000000">depends on the grid-fitting algo.</font>
|
||||
<p><b><font color="#000000">Inconsistency</font></b>
|
||||
<br><font color="#000000">results can vary between different renderers,
|
||||
or even distinct versions of the same engine.</font></center>
|
||||
</blockquote>
|
||||
</td>
|
||||
</tr>
|
||||
</table></center>
|
||||
</blockquote>
|
||||
|
||||
<center><table width="100%" border=0 cellpadding=5><tr bgcolor="#CCFFCC" valign=center>
|
||||
<td align=center width="30%">
|
||||
<a href="glyphs-1.html">Previous</a>
|
||||
</td>
|
||||
<td align=center width="30%">
|
||||
<a href="index.html">Contents</a>
|
||||
</td>
|
||||
<td align=center width="30%">
|
||||
<a href="glyphs-3.html">Next</a>
|
||||
</td>
|
||||
</tr></table></center>
|
||||
|
||||
</td></tr></table></center>
|
||||
</body>
|
||||
</html>
|
||||
|
|
|
|||
Loading…
Reference in New Issue