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playwright/tests/image_tools/fixtures/should-match/tiny-antialiasing-sample/README.md

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feat: implement a new image comparison function (#19166) This patch implements a new image comparison function, codenamed "ssim-cie94". The goal of the new comparison function is to cancel out browser non-determenistic rendering. To use the new comparison function: ```ts await expect(page).toHaveScreenshot({ comparator: 'ssim-cie94', }); ``` As of Nov 30, 2022, we identified the following sources of non-determenistic rendering for Chromium: - Anti-aliasing for certain shapes might be different due to the way skia rasterizes certain shapes. - Color blending might be different on `x86` and `aarch64` architectures. The new function employs a few heuristics to fight these differences. Consider two non-equal image pixels `(r1, g1, b1)` and `(r2, g2, b2)`: 1. If the [CIE94] metric is less then 1.0, then we consider these pixels **EQUAL**. (The value `1.0` is the [just-noticeable difference] for [CIE94].). Otherwise, proceed to next step. 1. If all the 8 neighbors of the first pixel match its color, or if the 8 neighbors of the second pixel match its color, then these pixels are **DIFFERENT**. (In case of anti-aliasing, some of the direct neighbors have to be blended up or down.) Otherwise, proceed to next step. 1. If SSIM in some locality around the different pixels is more than 0.99, then consider this pixels to be **EQUAL**. Otherwise, mark them as **DIFFERENT**. (Local SSIM for anti-aliased pixels turns out to be very close to 1.0). [CIE94]: https://en.wikipedia.org/wiki/Color_difference#CIE94 [just-noticeable difference]: https://en.wikipedia.org/wiki/Just-noticeable_difference
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# Tiny anti-aliasing sample
This is a 10x10 image sample with a 3 anti-aliased pixels in-between. This is actually
chore: fix typos (#20473)
2023-01-30 09:53:28 +01:00
a cropped down snapshot of one of the [ubuntu-x86-vs-ubuntu-arm samples](../ubuntu-x86-vs-ubuntu-arm/samples/stylings_stories-Stylings-stories-Texture-bar-should-use-custom-path-chrome/stylings-stories/texture/bar/should-use-custom-path-actual.png) handy for debugging
feat: implement a new image comparison function (#19166) This patch implements a new image comparison function, codenamed "ssim-cie94". The goal of the new comparison function is to cancel out browser non-determenistic rendering. To use the new comparison function: ```ts await expect(page).toHaveScreenshot({ comparator: 'ssim-cie94', }); ``` As of Nov 30, 2022, we identified the following sources of non-determenistic rendering for Chromium: - Anti-aliasing for certain shapes might be different due to the way skia rasterizes certain shapes. - Color blending might be different on `x86` and `aarch64` architectures. The new function employs a few heuristics to fight these differences. Consider two non-equal image pixels `(r1, g1, b1)` and `(r2, g2, b2)`: 1. If the [CIE94] metric is less then 1.0, then we consider these pixels **EQUAL**. (The value `1.0` is the [just-noticeable difference] for [CIE94].). Otherwise, proceed to next step. 1. If all the 8 neighbors of the first pixel match its color, or if the 8 neighbors of the second pixel match its color, then these pixels are **DIFFERENT**. (In case of anti-aliasing, some of the direct neighbors have to be blended up or down.) Otherwise, proceed to next step. 1. If SSIM in some locality around the different pixels is more than 0.99, then consider this pixels to be **EQUAL**. Otherwise, mark them as **DIFFERENT**. (Local SSIM for anti-aliased pixels turns out to be very close to 1.0). [CIE94]: https://en.wikipedia.org/wiki/Color_difference#CIE94 [just-noticeable difference]: https://en.wikipedia.org/wiki/Just-noticeable_difference
2022-12-03 00:22:05 +01:00
purposes.
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