colr-gradients-spec VS imageworsener

They just extended the COLR spec to COLRv1 which essentially is a whole new canvas API in fonts: https://github.com/googlefonts/colr-gradients-spec/blob/main...

There's a proposal for a new version that has a much richer imaging model: https://github.com/googlefonts/colr-gradients-spec

Otherwise, compress the images more. https://entropymine.com/imageworsener/ is a versatile multitool with a learning curve. Many image editors have support for downscaling images and compressing JPEGs. pngquant is a PNG-specific tool, if you like PNGs a lot.

There can be various causes for those symptoms:

1. Even if the rendering gets the subpixel order right, the subpixels are rarely equidistant on a display. They tend to be closer to each other within a logical pixel.

2. Some subpixel-AA algorithms are naive, and trade color accuracy to luminance accuracy, causing more color fringes.

3. Incorrect gamma handling.

4. If aiming for more luminance accuracy, incorrectly taking into account the relative luminance of the subpixels (what you observed with the brighter green subpixels).

Imageworsener[1] has an option to downscale with subpixel antialiasing, it's gamma correct by default, and it has an option for adjusting the subpixel offsets within a pixel (instead of the naive default of 1/3). It might be a good way to try out correct subpixel-AA, but it only works on images. I guess you can render text on high resolution and downscale that with imageworsener, but you won't get any hinting that way, but maybe that's desired.

Very few software does AA correctly, let alone subpixel-AA.

[1] https://entropymine.com/imageworsener/