Convert black to opaque and white to transparent. (Depends on pypng)
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import png | |
def convert(fin, fout): | |
reader = png.Reader(filename=fin) | |
width, height, pixels, metadata = reader.asDirect() | |
#print metadata | |
out = list() | |
for row in pixels: | |
row_out = list() | |
for i in xrange(0, width * metadata['planes'], metadata['planes']): | |
if metadata['planes'] < 3: # L or LA | |
alpha = row[i] | |
else: # RGB or RGBA | |
red, green, blue = row[i], row[i+1], row[i+2] | |
alpha = red * 0.3 + green * 0.59 + blue * 0.11 | |
alpha = 255 - alpha | |
if metadata['planes'] == 2 or metadata['planes'] == 4: | |
alpha = alpha * row[i+metadata['planes']-1] / 255.0 | |
alpha = max(0, min(int(alpha + 0.5), 255)) | |
row_out.append(0) # luma | |
row_out.append(alpha) # alpha | |
out.append(row_out) | |
writer = png.Writer(width=width, height=height, greyscale=True, alpha=True, compression=9) | |
with open(fout, 'w') as fp: | |
writer.write(fp, out) | |
import sys | |
import os.path | |
import getopt | |
LIGHTNESS = 0 | |
AVERAGE = 1 | |
LUMINOSITY = 2 | |
algo = LUMINOSITY | |
fin = None | |
fout = None | |
opts = getopt.getopt(sys.argv[1:], 'a:i:o:', ['algorithm=', 'input=', 'output=']) | |
for a, o in opts[0]: | |
if a in ('-a', '--algorithm'): | |
algo = o | |
elif a in ('-i', '--input'): | |
fin = os.path.abspath(o) | |
elif a in ('-o', '--output'): | |
fout = os.path.abspath(o) | |
if fin and os.path.exists(fin): | |
if not fout: | |
name, ext = os.path.splitext(fin) | |
fout = '%s_a%s' % (name, ext) | |
convert(fin, fout) |
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