The `Bitmap` type was referring to to its internal pixel format by a
name that represents the order of the color components as they are layed
out in memory. Contrary, the `Color` type was using a naming that where
the name represents the order of the components from most to least
significant byte when viewed as a unsigned 32bit integer. This is
confusing as you have to keep remembering which mental model to use
depending on which code you work with.
To unify the two, the naming of RGBA-like colors in the `Color` type has
been adjusted to match the one from the Bitmap type. This seems to be
generally in line with how web APIs think about these types:
* `ImageData.pixelFormat` can be `rgba-8unorm` backed by a
`Uint8ClamedArray`, but there is no pixel format backed by a 32bit
unsigned type.
* WebGL can use format `RGBA` with type `UNSIGNED_BYTE`, but there is no
such format with type `UNSIGNED_INT`.
Additionally, it appears that other browsers and browser-adjacent
libraries also think similarly about these types:
* Firefox:
https://github.com/mozilla-firefox/firefox/blob/main/gfx/2d/Types.h
* WebKit:
https://github.com/WebKit/WebKit/blob/main/Source/WebCore/platform/graphics/PixelFormat.h
* Skia:
https://chromium.googlesource.com/skia/+/refs/heads/main/include/core/SkColorType.h
This has the not so nice side effect that APIs that interact with these
types through 32bit unsigned integers now have the component order
inverted due to little-endian byte order. E.g. specifying a color as hex
constant needs to be done as `0xAABBGGRR` if it is to be treated as
RGBA8888.
We could alleviate this by providing endian-independent APIs to callers.
But I suspect long-term we might want to think differently about bitmap
data anyway, e.g. to better support HDR in the future. However, such
changes would be more involved than just unifying the naming as done
here. So I considered that out of scope for now.
Our Color::to_premultiplied() and Color::to_unpremultiplied() used
integer truncation.
Apple’s Accelerate framework (and many other libraries) use
round-to-nearest, which avoids bias and produces results that differ
by ±1 in many cases.
This commit switches both helpers to round-to-nearest and clamps the
results to [0,255]. For alpha==0 we now return fully transparent black
(0,0,0,0) to align with common conventions, instead of preserving RGB.
The current Color::interpolate_color method does not follow the specs
properly. Started improving it by handling premultiplied alpha in color
interpolation.
Only one WPT test covers this (color-transition-premultiplied), which we
currently pass due to a different approach in Color.mixed_with.
Bitmap::get_pixel() was only handling two out of the four possible pixel
formats, asserting when called with the other two. The asserting code
path was triggered when loading JPEG XL images, causing crashes on pages
like https://jpegxl.info/resources/jpeg-xl-test-page or
https://html5test.co/.
When decoding data into bitmaps, we end up with different alpha types
(premultiplied vs. unpremultiplied color data). Unfortunately, Skia only
seems to handle premultiplied color data well when scaling bitmaps with
an alpha channel. This might be due to Skia historically only supporting
premultiplied color blending, with unpremultiplied support having been
added more recently.
When using Skia to blend bitmaps, we need the color data to be
premultiplied. ImmutableBitmap gains a new method to enforce the alpha
type to be used, which is now used by SharedResourceRequest and
CanvasRenderingContext2D to enforce the right alpha type.
Our LibWeb tests actually had a couple of screenshot tests that exposed
the graphical glitches caused by Skia; see the big smiley faces in the
CSS backgrounds tests for example. The failing tests are now updated to
accommodate the new behavior.
Chromium and Firefox both seem to apply the same behavior; e.g. they
actively decode PNGs (which are unpremultiplied in nature) to a
premultiplied bitmap.
Fixes#3691.
- Hue now wraps properly when negative or larger than 360
- The hsl to rgb conversion now closely mirrors the code example from
the spec.
This fixes a number of WPT tests in
/css/css-color/parsing/color-computed-hsl.html
This color space is often used as a reference in WPT tests, having
support for it makes us pass 15 new tests:
- css/css-color/rec2020-001.html
- css/css-color/rec2020-002.html
- css/css-color/rec2020-003.html
- css/css-color/rec2020-004.html
- css/css-color/rec2020-005.html
- css/css-color/predefined-011.html
- css/css-color/predefined-012.html
That makes us pass the following WPT tests:
- css/css-color/prophoto-rgb-001.html
- css/css-color/prophoto-rgb-002.html
- css/css-color/prophoto-rgb-003.html
- css/css-color/prophoto-rgb-004.html
- css/css-color/prophoto-rgb-005.html
- css/css-color/predefined-009.html
- css/css-color/predefined-010.html
This color space is often used as a reference in WPT tests, having
support for it makes us pass 15 new tests:
- css/css-color/display-p3-001.html
- css/css-color/display-p3-002.html
- css/css-color/display-p3-003.html
- css/css-color/display-p3-004.html
- css/css-color/display-p3-005.html
- css/css-color/display-p3-006.html
- css/css-color/lab-008.html
- css/css-color/lch-008.html
- css/css-color/oklab-008.html
- css/css-color/oklch-008.html
- css/css-color/predefined-005.html
- css/css-color/predefined-006.html
- css/css-color/xyz-005.html
- css/css-color/xyz-d50-005.html
- css/css-color/xyz-d65-005.html
This makes us pass the following WPT tests:
- css/css-color/a98rgb-001.html
- css/css-color/a98rgb-002.html
- css/css-color/a98rgb-003.html
- css/css-color/a98rgb-004.html
- css/css-color/predefined-007.html
- css/css-color/predefined-008.html
Problem:
- Functions are duplicated in [PBM,PGM,PPM]Loader class
implementations. They are functionally equivalent. This does not
follow the DRY (Don't Repeat Yourself) principle.
Solution:
- Factor out the common functions into a separate file.
- Refactor common code to generic functions.
- Change `PPM_DEBUG` macro to be `PORTABLE_IMAGE_LOADER_DEBUG` to work
with all the supported types. This requires adding the image type to
the debug log messages for easier debugging.
Switch over to gamma-aware interpolation. This causes color gradients
to not look so dark in the middle. SIMD optimized code is provided for
sse1 enabled builds.
Fixes#1342.
Problem:
- `constexpr` functions are decorated with the `inline` specifier
keyword. This is redundant because `constexpr` functions are
implicitly `inline`.
- [dcl.constexpr], §7.1.5/2 in the C++11 standard): "constexpr
functions and constexpr constructors are implicitly inline (7.1.2)".
Solution:
- Remove the redundant `inline` keyword.
Instead of passing the BufferStream, pass the Decoder. I'd like to stop
using BufferStream eventually anyway, so it's good to get it out of any
API's where it's in currently.
This shaves ~5 seconds off of a full build, not too bad. Also it just
seems nicer to push this logic out to classes. It could be better but
it's a start. :^)
