[autofit] Document warper.
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@ -1152,6 +1152,8 @@
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#ifdef AF_USE_WARPER
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#ifdef AF_USE_WARPER
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/* Apply (small) warp scale and warp delta for given dimension. */
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FT_LOCAL_DEF( void )
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FT_LOCAL_DEF( void )
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af_glyph_hints_scale_dim( AF_GlyphHints hints,
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af_glyph_hints_scale_dim( AF_GlyphHints hints,
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AF_Dimension dim,
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AF_Dimension dim,
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@ -4,7 +4,7 @@
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/* */
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/* */
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/* Auto-fitter warping algorithm (body). */
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/* Auto-fitter warping algorithm (body). */
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/* */
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/* */
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/* Copyright 2006, 2007 by */
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/* Copyright 2006, 2007, 2011 by */
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/* David Turner, Robert Wilhelm, and Werner Lemberg. */
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/* David Turner, Robert Wilhelm, and Werner Lemberg. */
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/* */
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/* */
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/* This file is part of the FreeType project, and may only be used, */
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/* This file is part of the FreeType project, and may only be used, */
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@ -16,10 +16,20 @@
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/***************************************************************************/
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/***************************************************************************/
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/*
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* The idea of the warping code is to slightly scale and shift a glyph
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* within a single dimension so that as much of its segments are aligned
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* (more or less) on the grid. To find out the optimal scaling and
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* shifting value, various parameter combinations are tried and scored.
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*/
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#include "afwarp.h"
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#include "afwarp.h"
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#ifdef AF_USE_WARPER
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#ifdef AF_USE_WARPER
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/* The weights cover the range 0/64 - 63/64 of a pixel. Obviously, */
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/* values around a half pixel (which means exactly between two grid */
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/* lines) gets the worst weight. */
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#if 1
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#if 1
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static const AF_WarpScore
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static const AF_WarpScore
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af_warper_weights[64] =
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af_warper_weights[64] =
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@ -43,6 +53,11 @@
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#endif
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#endif
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/* Score segments for a given `scale' and `delta' in the range */
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/* `xx1' to `xx2', and store the best result in `warper'. If */
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/* the new best score is equal to the old one, prefer the */
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/* value with a smaller distortion (around `base_distort'). */
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static void
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static void
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af_warper_compute_line_best( AF_Warper warper,
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af_warper_compute_line_best( AF_Warper warper,
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FT_Fixed scale,
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FT_Fixed scale,
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@ -100,6 +115,7 @@
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FT_Int idx;
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FT_Int idx;
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/* score the length of the segments for the given range */
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for ( idx = idx_min; idx <= idx_max; idx++, y++ )
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for ( idx = idx_min; idx <= idx_max; idx++, y++ )
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scores[idx] += af_warper_weights[y & 63] * len;
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scores[idx] += af_warper_weights[y & 63] * len;
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}
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}
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@ -115,9 +131,9 @@
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AF_WarpScore distort = base_distort + ( idx - idx0 );
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AF_WarpScore distort = base_distort + ( idx - idx0 );
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if ( score > warper->best_score ||
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if ( score > warper->best_score ||
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( score == warper->best_score &&
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( score == warper->best_score &&
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distort < warper->best_distort ) )
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distort < warper->best_distort ) )
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{
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{
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warper->best_score = score;
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warper->best_score = score;
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warper->best_distort = distort;
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warper->best_distort = distort;
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}
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}
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/* Compute optimal scaling and delta values for a given glyph and */
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/* dimension. */
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FT_LOCAL_DEF( void )
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FT_LOCAL_DEF( void )
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af_warper_compute( AF_Warper warper,
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af_warper_compute( AF_Warper warper,
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AF_GlyphHints hints,
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AF_GlyphHints hints,
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@ -215,6 +234,7 @@
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warper->t1 = AF_WARPER_FLOOR( warper->x1 );
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warper->t1 = AF_WARPER_FLOOR( warper->x1 );
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warper->t2 = AF_WARPER_CEIL( warper->x2 );
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warper->t2 = AF_WARPER_CEIL( warper->x2 );
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/* examine a half pixel wide range around the maximum coordinates */
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warper->x1min = warper->x1 & ~31;
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warper->x1min = warper->x1 & ~31;
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warper->x1max = warper->x1min + 32;
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warper->x1max = warper->x1min + 32;
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warper->x2min = warper->x2 & ~31;
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warper->x2min = warper->x2 & ~31;
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warper->x2min = warper->x2;
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warper->x2min = warper->x2;
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}
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}
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/* examine (at most) a pixel wide range around the natural width */
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warper->wmin = warper->x2min - warper->x1max;
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warper->wmin = warper->x2min - warper->x1max;
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warper->wmax = warper->x2max - warper->x1min;
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warper->wmax = warper->x2max - warper->x1min;
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#if 1
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#if 1
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/* some heuristics to reduce the number of widths to be examined */
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{
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{
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int margin = 16;
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int margin = 16;
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@ -273,6 +295,8 @@
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FT_Pos xx1, xx2;
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FT_Pos xx1, xx2;
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/* compute min and max positions for given width, */
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/* assuring that they stay within the coordinate ranges */
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xx1 = warper->x1;
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xx1 = warper->x1;
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xx2 = warper->x2;
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xx2 = warper->x2;
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if ( w >= warper->w0 )
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if ( w >= warper->w0 )
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@ -304,6 +328,7 @@
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else
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else
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base_distort += xx2 - warper->x2;
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base_distort += xx2 - warper->x2;
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/* give base distortion a greater weight while scoring */
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base_distort *= 10;
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base_distort *= 10;
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new_scale = org_scale + FT_DivFix( w - warper->w0, X2 - X1 );
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new_scale = org_scale + FT_DivFix( w - warper->w0, X2 - X1 );
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@ -331,7 +356,7 @@
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#else /* !AF_USE_WARPER */
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#else /* !AF_USE_WARPER */
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char af_warper_dummy = 0; /* make compiler happy */
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char af_warper_dummy = 0; /* make compiler happy */
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#endif /* !AF_USE_WARPER */
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#endif /* !AF_USE_WARPER */
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