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Fix unexpected error when saving zero dimension images #9391

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Fix unexpected error when saving zero dimension images #9391

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@radarhere radarhere commented Jan 12, 2026 •
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#9389 has pointed out that

from PIL import Image
img = Image.new('RGB', (0, 50))
img.save('test.gif')

raises

Traceback (most recent call last):
  File "demo.py", line 3, in <module>
    img.save('test.gif')
  File "PIL/Image.py", line 2592, in save
    save_handler(self, fp, filename)
  File "PIL/GifImagePlugin.py", line 808, in _save
    _write_single_frame(im, fp, palette)
  File "PIL/GifImagePlugin.py", line 625, in _write_single_frame
    im_out = _normalize_palette(im_out, palette, im.encoderinfo)
  File "PIL/GifImagePlugin.py", line 599, in _normalize_palette
    optimized_palette_colors = _get_optimize(im, info)
  File "PIL/GifImagePlugin.py", line 959, in _get_optimize
    if optimise or max(used_palette_colors) >= len(used_palette_colors):
ValueError: max() arg is an empty sequence

There is also an unexpected error for SPIDER images.

from PIL import Image
img = Image.new('RGB', (0, 50))
img.save('test', 'SPIDER')

raises

Traceback (most recent call last):
  File "demo.py", line 3, in <module>
    im.save('out', 'SPIDER')
  File "PIL/Image.py", line 2592, in save
    save_handler(self, fp, filename)
  File "PIL/SpiderImagePlugin.py", line 296, in _save_spider
    _save(im, fp, filename)
  File "PIL/SpiderImagePlugin.py", line 279, in _save
    hdr = makeSpiderHeader(im)
  File "PIL/SpiderImagePlugin.py", line 248, in makeSpiderHeader
    labrec = int(1024 / lenbyt)
ZeroDivisionError: division by zero

This fixes thse unexpected errors, instead raising

Traceback (most recent call last):
  File "demo.py", line 3, in <module>
    img.save('test.gif')
  File "PIL/Image.py", line 2592, in save
    save_handler(self, fp, filename)
  File "PIL/GifImagePlugin.py", line 808, in _save
    _write_single_frame(im, fp, palette)
  File "PIL/GifImagePlugin.py", line 637, in _write_single_frame
    ImageFile._save(
  File "PIL/ImageFile.py", line 662, in _save
    _encode_tile(im, fp, tile, bufsize, fh)
  File "PIL/ImageFile.py", line 682, in _encode_tile
    encoder.setimage(im.im, extents)
SystemError: tile cannot extend outside image

There is also an unexpected error for PCX images.

from PIL import Image
img = Image.new('RGB', (0, 50))
img.save('test.pcx')

raises

Traceback (most recent call last):
  File "demo.py", line 15, in <module>
    img.save('test.pcx')
  File "PIL/Image.py", line 2592, in save
    save_handler(self, fp, filename)
  File "PIL/PcxImagePlugin.py", line 185, in _save
    + o16(im.size[0] - 1)
  File "PIL/_binary.py", line 100, in o16le
    return pack("<H", i)
struct.error: ushort format requires 0 <= number <= (32767 * 2 + 1)

This adds a new error, similar to JPEG

Traceback (most recent call last):
  File "demo.py", line 15, in <module>
    img.save('test.pcx')
  File "PIL/Image.py", line 2592, in save
    save_handler(self, fp, filename)
  File "PIL/PcxImagePlugin.py", line 151, in _save
    raise ValueError(msg)
ValueError: Cannot write empty image as PCX

@radarhere radarhere added the GIF label Jan 12, 2026
@radarhere radarhere mentioned this pull request Jan 12, 2026
Closed
@radarhere radarhere removed the GIF label Jan 12, 2026
@radarhere radarhere changed the title Fix unexpected error when saving zero dimension GIF Fix unexpected error when saving zero dimension GIF and PCX Jan 12, 2026
@radarhere radarhere force-pushed the gif_save branch 2 times, most recently from 876be85 to 4326110 Compare January 12, 2026 21:48
@radarhere radarhere changed the title Fix unexpected error when saving zero dimension GIF and PCX Fix unexpected error when saving zero dimension images Jan 13, 2026
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