From 78466698fc2eface6ae3f087b2ef7f36b774b408 Mon Sep 17 00:00:00 2001
From: Niles Rogoff <nilesrogoff@gmail.com>
Date: Mon, 11 Jul 2016 11:15:59 -0400
Subject: [PATCH] Added dithering, added documentation for dithering and bits
 per color, vastly simplified test suite by abstracting control logic to
 another function, added tests for dithering, removed debug info

---
 2bit.py     | 25 ++++++++++++-------------
 README.md   |  4 +++-
 test/run.py | 36 ++++++++++++++++++++++++++++--------
 3 files changed, 43 insertions(+), 22 deletions(-)

diff --git a/2bit.py b/2bit.py
index 015e0ea..b6c7ecb 100644
--- a/2bit.py
+++ b/2bit.py
@@ -1,18 +1,21 @@
 bits = 2
 outfile = "out.png"
-print_debug = False
 per_color = False
+dither = False
 
 # End of the configuration section
 
-import PIL.Image, sys
+import PIL.Image, sys, random
 if len(sys.argv) >= 3:
     outfile = sys.argv[2]
 if len(sys.argv) >= 4:
     bits = int(sys.argv[3])
-per_color = "--per-color" in [f.lower() for f in sys.argv]
-def debug(*args):
-    if print_debug: print(*args)
+args = [f.lower() for f in sys.argv]
+if "--dither" in args:
+    dither = float(args[args.index("--dither") + 1].replace("%",""))
+if dither > 1:
+    dither /= 100
+per_color = "--per-color" in args
 def binprecision(start, bits, length):
     end = bin(int(start))[2:]
     while len(end) < bits:
@@ -26,25 +29,21 @@ elif bits == 1:
     mode = "1" # 1x1 bit unsigned integer
 out = PIL.Image.new(mode,image.size)
 colors = [int(i*255.0/(2**bits-1)) for i in range(2**bits)]
-debug(image.width, image.height)
 for x in range(image.width):
     for y in range(image.height):
         pos = (x,y)
         color = image.getpixel(pos)
-        debug(color)
         if len(color) == 4:
             color = color[:3] # Exclude alpha layer
         color = list(color)
         if not per_color:
             color = [float(sum(color))/len(color)]
-        debug(color)
-        for z in color: debug(bin(int(z)))
         for z in range(len(color)):
+            if dither:
+                color[z] += 255 * random.uniform(-dither,dither)
+                color[z] = min(color[z], 255)
+                color[z] = max(color[z], 0)
             index = int(binprecision(color[z], 8, bits), 2)
-            debug(index)
             color[z] = colors[index]
         out.putpixel(pos, tuple(color))
-        debug()
-    debug("------------")
-    debug()
 out.save(outfile)
diff --git a/README.md b/README.md
index b3cdc6a..36e72d5 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,9 @@
 
 Inspired by [2bit](http://2bit.neocities.org/)
 
-Usage: `python3 2bit.py infile.png [outfile.png] [bits]`
+Usage: `python3 2bit.py infile.png [outfile.png] [bits] [--per-color] [--dither dither_value]`
+
+dither\_value can be like `50%`, `50` or `.5`
 
 Warning: Will probably turn transparency black
 
diff --git a/test/run.py b/test/run.py
index 10d3f3e..de57387 100644
--- a/test/run.py
+++ b/test/run.py
@@ -8,19 +8,39 @@ files = glob.glob("*")
 del files[files.index("run.py")]
 if not os.path.isdir("out"): os.mkdir("out")
 i = 0
-max_i = len(files) * (8+8)
+max_i = len(files) * (16*3)
+
+def getparams(i):
+    percolor = dither = False
+    if i % 16 >= 8:
+        percolor = True
+    if i >= 16:
+        dither = '15'
+    if i >= 32:
+        dither = '50'
+    return percolor, dither
+
 for f in files:
     if (os.path.isdir(f)): continue
-    for bits in range(8+8):
+    if (f[-3:]) == '.py': continue
+    for bits in range(16*3):
         bits += 1
-        percolor = []
-        pc = ""
-        if bits > 8:
+        percolor, dither = getparams(i)
+        if not percolor:
+            percolor = []
+            pc = ""
+        else:
             percolor = ["--per-color"]
-            pc = "-per-color"
+            pc = "per-color-"
+        if not dither:
+            dither = []
+            dc = ""
+        else:
+            dc = "dither-" + dither + "%-"
+            dither = ["--dither", dither]
         print(str(int(float(1000*i)/max_i)/10) + "% done")
         bits_formatted = str((bits-1)%8+1)
-        outfilename = "out/" + ".".join(f.split(".")[:-1]) + "-output" + pc + "-" + bits_formatted + "bits.png"
+        outfilename = "out/" + ".".join(f.split(".")[:-1]) + "-output-" + pc + dc + bits_formatted + "bits.png"
         print("On " + outfilename)
-        subprocess.call(["python3", "../2bit.py", f, outfilename, bits_formatted, *percolor])
+        subprocess.call(["python3", "../2bit.py", f, outfilename, bits_formatted, *percolor, *dither])
         i += 1