ICO: Add support for different color depths per icon size

[gonzoMD]

What did you do?

I took a bunch of pngs of different sizes and wanted to convert them to ICO with different color depths per size

What did you expect to happen?

that I add different images (in terms of color depth) and their sizes to a list and the different images will put into one icon

What actually happened?

there are multiple images of a size added, but all of them are the the same, the last added image

What are your OS, Python and Pillow versions?

• OS: Kubuntu 21.10
• Python: Python 3.9.7 (default, Sep 10 2021, 14:59:43)
• Pillow: 8.1.2

from PIL import Image

images=[]
sizes=[]

#save an icon with three time the same 48x48px image
images.append(Image.open("test.png"))
sizes.append((48,48))
images.append(Image.open("test.png"))
sizes.append((48,48))
images.append(Image.open("test.png"))
sizes.append((48,48))

im = Image.new(mode="RGBA", size=(48,48))
im.save("good.ico", format="ICO", sizes = sizes, append_images = images, bitmap_format="bmp")

images=[]
sizes=[]

#save an icon with three different 48x48px image
images.append(Image.open("test.png")) #original image
sizes.append((48,48))
images.append(Image.new(mode="P", size=(48,48))) # palette image, default bg color
sizes.append((48,48))
images.append(Image.new(mode="P", size=(48,48), color="#ff00ff"))
sizes.append((48,48))

im = Image.new(mode="RGBA", size=(48,48))
im.save("bad.ico", format="ICO", sizes = sizes, append_images = images, bitmap_format="bmp")

I added a zip with an example
test.zip
.

[nulano]

Just to link to it, this is a continuation of #6120.

[radarhere]

I would think that the last two images you are adding - Image.new(mode="P", size=(48,48)) and Image.new(mode="P", size=(48,48), color="#ff00ff") - are the same color depth. Do you agree?

Even if the specification did allow for multiple images of the same size and same color depth, that doesn't sound like it would be useful.

[gonzoMD]

Yes, they are. What I want to show here is that the first image, the one opened from file, is not added.

[radarhere]

I've created PR #6122 to resolve this.