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GIF - use single colour table for all frames #3788
Description
What did you do?
Attempted to normalise a sequence of P images to use the same colour palette in an attempt to output a smaller GIF file that uses a common palette across all frames.
The complete code is here - https://github.com/pimoroni/mlx90640-library/blob/master/python/rgb-to-gif.py - but the relevant snippet can be found below:
if len(frames) > 1:
# Generate an image with all frames, and crunch it to ADAPTIVE to form a master colour palette
master = Image.new('RGB', (32, 24 * len(frames)))
for index, image in enumerate(frames):
master.paste(image, (0, 24 * index))
master = master.convert('P', dither=False, palette=Image.ADAPTIVE, colors=256)
for index, image in enumerate(frames):
image = image.convert('P', dither=False, palette=master.palette)
# image = image.quantize(method=3, palette=master)
image = image.transpose(Image.ROTATE_270).transpose(Image.FLIP_LEFT_RIGHT)
image = image.resize(OUTPUT_SIZE, Image.NEAREST)
frames[index] = image
filename = 'mlx90640-{}.gif'.format(
datetime.now().strftime("%Y-%m-%d-%H-%M-%S"))
print("Saving {} with {} frames.".format(filename, len(frames)))
frames[0].save(
filename,
save_all=True,
append_images=frames[1:],
duration=1000 // fps,
loop=0,
include_color_table=True,
optimize=True,
palette=master.palette.getdata())What did you expect to happen?
For the GIF format save method to understand that I was sharing a colour palette across frames, and export accordingly. There doesn't seem to be a way - that I can identify - to communicate this.
What actually happened?
Result a ~1.19MiB GIF:
Versus a ~263.4KiB GIF - This is a ~70-80% size saving just running the result through ezgif (https://ezgif.com/optimize) optimisation and picking "Use single color table for all frames":
Unless I am very much misunderstanding what ezgif is doing in this case, no other optimisation was performed.
What are your OS, Python and Pillow versions?
- OS: Linux, Raspbia
- Python: 3.4.9
- Pillow: PIL.PILLOW_VERSION == 5.4.1
Activity
radarhere commentedon Jul 1, 2021
Taking your 1.2mb image, and running
Before #5291, the output is 1.3mb. After, it is 320kb.
So we're not using a single color table yet, but that is a step towards solving your underlying problem.
radarhere commentedon Jul 11, 2021
I've created #5603 to resolve this. With it, this code produces a 281kb file, down from the 320kb file from the code in my last post.
Gadgetoid commentedon Jul 11, 2021
That's mighty close to the output I got above, and a considerable size reduction! Amazing. Thank you for taking the time to do this- it would have taken me forever just to figure out how to figure out how.