Fails to decode tga image with "Image is too large" error

[FredrikNoren]

Expected

The image I've attached should load

Actual behaviour

I'm getting an error: "Image is too large"

Reproduction steps

Simply load the attached image with image.

Crossbow_Ao.tga.zip

[fintelia]

The error is being triggered here:

image/src/codecs/tga/decoder.rs

Lines 477 to 481 in b02bb74

	if pixel_data.len() != buf.len() {
	return Err(ImageError::Limits(LimitError::from_kind(
	LimitErrorKind::DimensionError,
	)));
	}

pixel_data.len() = 3 * 4096 * 4096 and buf.len() = 4 * 4096 * 4096.

[fintelia]

Ok, the issue seems to be that the image header has Image Descriptor Byte set to 8, but the color map itself only contains RGB data. This source claims that "This entire byte should be set to 0" for color mapped data, but I'm not sure that's the authoritative spec. Perhaps the right thing is actually just to ignore that byte for color mapped images and just derive the presence of an alpha channel from the number of bytes per color map entry?