Downscale images before embedding #4609
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| // We use sqrt because scaling affects both dimensions | ||
| const sizeRatio = MAX_IMAGE_SIZE_BYTES / imageBytes.length; | ||
| // Be conservative: target 80% of max size to account for compression variance | ||
| let scaleFactor = Math.sqrt(sizeRatio * 0.8); |
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Need to think through if this square root thing is actually right... 🤔
You have a 4x4 image = 16 pixels = (let's pretend one byte per pixel, uncompressed) = 16 bytes
You want to halve the size to 8 bytes
If you simply halve the width & height to 2x2, you'll get 4 pixels = 4 times smaller than 16 bytes
Whereas if you scale width & height by 1/sqrt(2) you get:
about 2.8 * 2.8 = 7.84 = about 8
OK I get it!
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Brute force seems the only way to ensure they will fall below certain filesize indeed. Sharp is a good choice (based on Vips) if lambda can haz any. Without either reading about model behaviour with different resolution/compression and other characteristics (eg. does transparency even matter?) or doing a lot of tests, it’s impossible to know what are the best compromises (better larger and more compressed or the other way around? fine to bake transparency into JPEGs or is transparency taken seriously? etc). One thing I can’t think wouldn’t be sensible is to convert everything to sRGB (this, I think). |
Depends on #4608, currently diffed to that branch
how to test
npm run test:integrationand see the large image tests now pass