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jtippet edited this page Mar 23, 2019 · 1 revision

ICO421: BitmapMaskWrongColors

When storing a bitmap in an ICO file, the ICO file also requires a mask. The mask specifies which pixels are transparent: both for painting, and also possibly for hit-testing. For example, if the user clicks on a masked-out pixel of an icon, the GUI framework might choose to ignore the click.

When adding a frame to an icon, you can provide your own mask. The mask format used inside an ICO file is difficult to generate using common image-editing software, so for your convenience, the IcoTools suite accepts a mask that is itself encoded as a bitmap file. If you provide a mask this way, though, the bitmap file must only have two colors in it: pure black and pure white. Nothing else can be converted into an ICO mask, since each pixel of an ICO mask is always 1-bit: fully opaque or fully transparent.

Double-check that the mask you've provided contains only black and white pixels.

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