.ICO and .CUR format support #241

edqx · 2025-03-16T15:45:46Z

This is still early days, but I thought a PR would help to track this, and since I may need some help.

For now, I'm just using the Wikipedia page for .ICO as a reference: https://en.wikipedia.org/wiki/ICO_(file_format)#Icon_file_structure.

Blockage 1

The main blockage is that .ICO and .CUR files have entries with different sizes. Normally multiple images would be fine (see .gif files), however currently there's no support in zigimg for entries of various sizes. To get around this temporarily, I've just made any files without exactly 1 entry unsupported.

I am not sure whether different entry sizes is something maintainers of zigimg want or not, but it may be the case that .ICO and .CUR files are "out of scope" and should instead store multiple ImageUnmanaged.

Blockage 2

The second blockage is that the .BMP file format support has no support for the windows bitmap header:

zigimg/src/formats/bmp.zig

Line 58 in b0a046b

pub const BitmapInfoHeaderWindows31 = extern struct {

zigimg/src/formats/bmp.zig

Line 129 in b0a046b

windows31: BitmapInfoHeaderWindows31,

zigimg/src/formats/bmp.zig

Line 319 in b0a046b

else => return ImageUnmanaged.Error.Unsupported,

Presumably .ICO and .CUR files support other header formats for BMP, but since they're windows formats I still consider this to be a blockage.

This is a lot easier to fix than blockage 1, and I will probably just add it to this PR.

Notes

I've updated to Zig 0.14.0 because the Mach Nominated Zig version 2024.11.0-mach is no longer registered for zigup to download. I don't suppose this PR will be finished before the next nominated version, so I don't think this is a problem. (I'll continue to work on 0.14.0)

PS D:\Projects\zigimg> zigup 0.14.0-dev.2577+271452d22
install directory 'C:\Users\aquila\.zigup\zigup-v2025_01_02\zig'
mkdir "C:\Users\aquila\.zigup\zigup-v2025_01_02\zig"
rd /s /q "C:\Users\aquila\.zigup\zigup-v2025_01_02\zig\0.14.0-dev.2577+271452d22.installing"
mkdir "C:\Users\aquila\.zigup\zigup-v2025_01_02\zig\0.14.0-dev.2577+271452d22.installing"
downloading 'https://ziglang.org/builds/zig-windows-x86_64-0.14.0-dev.2577+271452d22.zip' to 'C:\Users\aquila\.zigup\zigup-v2025_01_02\zig\0.14.0-dev.2577+271452d22.installing\zig-windows-x86_64-0.14.0-dev.2577+271452d22.zip'
error: download 'https://ziglang.org/builds/zig-windows-x86_64-0.14.0-dev.2577+271452d22.zip' failed: HTTP server replied with unsuccessful response '404 Not Found'
rd /s /q "C:\Users\aquila\.zigup\zigup-v2025_01_02\zig\0.14.0-dev.2577+271452d22.installing"

mlarouche · 2025-03-16T17:36:16Z

Blockage 1

ICO is not the only image format with support for sub-images of different width and heights see #16 for instance. I think we would need to add another format-independant type alongside Image/ImageUnmanaged to support these multi-size images with their own read/write interface. For now just read/write the largest image format unless you want to provide that format-independant type. Even if we add a new format-independant type, Image/ImageUnmanaged should still support ICO and return the largest image.

Blockage 2

Yup BMP support is not complete so if you find an ICO or CUR that needs bitmap with version earlier than v4 or v5 please implement support for it :)

src/formats/ico.zig

edqx · 2025-03-16T19:54:40Z

What constitutes the 'largest image' in the set? The largest area, most bytes, greatest width, greatest height, etc?

mlarouche · 2025-03-16T19:58:19Z

What constitutes the 'largest image' in the set? The largest area, most bytes, greatest width, greatest height, etc?

Biggest width and height

…not reading into image

edqx · 2025-03-17T15:32:01Z

How do you want to handle converting between different pixel formats? My personal use case is to convert to ICO images, but they only really support BGRA32. Should converting (e.g., PNG -> ICO) be done automatically when writing to the format?

mlarouche · 2025-03-18T12:55:12Z

How do you want to handle converting between different pixel formats? My personal use case is to convert to ICO images, but they only really support BGRA32. Should converting (e.g., PNG -> ICO) be done automatically when writing to the format?

See the reply I put here: #231 (comment)

edqx · 2025-03-18T20:35:25Z

I think this is all that makes sense for me to do. I thought it would take longer, but the ICO format is simple enough and both PNG and BMP have a foundational implementation.

There's still some stuff missing, but a lot of it depends on BMP and PNG support, as well as supporting multiple entries as we talked about. This is enough for my use case (at least for now), and I don't want this PR to get out of scope. I'll likely be back another time with some more PRs as this library is fundamental to my project.

mlarouche · 2025-03-19T12:58:36Z

src/formats/ico.zig

+        return result;
+    }
+
+    pub fn largestEntryIdx(self: ICO) ?usize {


largestEntryIndex

mlarouche · 2025-03-19T13:04:33Z

Looking good so far, the only thing missing are tests, you can submit test images to this repo: https://github.com/zigimg/test-suite

…o ico-format

edqx · 2025-03-30T14:57:48Z

I'll finally add some tests this week, been busy. Not really sure where to get some good test images from, though.

edqx added 2 commits March 15, 2025 22:48

Fix compilation errors

780a43f

Add initial parsing for .ICO and .CUR files

016e33a

edqx marked this pull request as draft March 16, 2025 15:45

mlarouche reviewed Mar 16, 2025

View reviewed changes

src/formats/ico.zig Outdated Show resolved Hide resolved

Fix naming convention

1661838

edqx added 4 commits March 17, 2025 13:45

Fix improper use of buffered stream causing read artifacts

0441e0a

Use largest entry in ICO directory

56f6131

Attempt to read mask that resides after actual BMP data

66431b7

Remove requirement that only one entry is in the icon directory when …

aa8e4ff

…not reading into image

edqx added 6 commits March 18, 2025 15:01

Add initial writing .ICO files

a49cf5a

Handle buffered stream seek error properly

4481f9d

Add align(1) to the alpha of BGRA colours, to match RGBA colours

c5c46d2

Write no-op bits to ICO inner BMP image

82882a5

Minor cleanup of ICO format

655b79f

Update README for ICO support

64ac018

edqx marked this pull request as ready for review March 18, 2025 20:35

Improve defaults for BMP info header in ICO

3b53ec4

mlarouche reviewed Mar 19, 2025

View reviewed changes

src/formats/ico.zig Outdated

return result;

}

pub fn largestEntryIdx(self: ICO) ?usize {

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largestEntryIndex

edqx added 4 commits March 20, 2025 21:39

Use 'index' instead of 'idx' to better match Zig naming scheme

2af3d7c

Merge branch 'upstream' into ico-format

d67cf9d

Merge branch 'master' of https://github.com/MidlightStudio/zigimg int…

6e835db

…o ico-format

Remove IFF debugging

2dad8f8

Fix ICO using wrong PNG write signature, build error

a35c278

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.ICO and .CUR format support #241

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Blockage 1

Blockage 2

Notes

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mlarouche commented Mar 16, 2025

Blockage 1

Blockage 2

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