Only supported for plugins that set is_vector() to true. This returns
the frames as Gfx::VectorGraphics, which allows painting/rasterizing
them with arbitrary transforms and scales.
Both `decode_[header,image]_and_update_context()` used to take a
`Stream&` as parameter, but they are always called with the field
`m_context.stream` so no need to take it as a parameter.
This enum used to store very precise state about the decoding process,
let's simplify that by only including two steps: HeaderDecoder and
BitmapDecoded.
https://www.haiku-os.org/images/bg-page.png has a size of 0 for
example.
Just ignoring the chunk instead of assuming that the image is sRGB
and has Perceptual rendering intent matches what libpng does
(cf `png_handle_sRGB()`), so let's do that too.
(All other chunk handlers are still strict about size.)
In order to ease the removal of this function, let's provide a no-op
default implementation so decoders can stop implementing it one by one.
First step of #19893
The adobe specification doesn't even consider JPEG images with a single
component. So let's not consider the content of the App14 segment for
grayscale images.
This is clearly something I missed during the first implementation. The
specification is crystal clear about it: "The quantization elements
shall be specified in zig-zag scan order."
This patch fixes the weird behavior we had when using the quantization
table.
This adds a decoder for the TinyVG vector format (https://tinyvg.tech/).
TinyVG is a very simple binary vector format, but it is good enough to
represent a lot of SVGs, without needing the full web engine.
The main use case for Serenity is for scalable icons (which .tvg easily
handles).
The ideal size is the size the user will display the image. Raster
formats should ignore this parameter, but vector formats can use
it to generate a bitmap of the ideal size.
Decoding progressive JPEGs involves a much more complicated logic than
sequential JPEGs. Thanks to template specialization, this patch allow us
to skip the additional cost of progressive images when it's not needed.
It gives a nice 10% improvements on sequential JPEGs :^)
This solution is a middle ground between re-computing `cos` every time
and a much more mathematically complicated approach (as we have in the
decoder).
While still being far from optimal it already gives us a 10x
improvement, not that bad :^)
Co-authored-by: Tim Flynn <trflynn89@pm.me>
This encoder is very naive as it only output SOF0 images and uses
pre-defined Huffman tables.
There is also a small bug with quantization which make using it
over-degrade the quality.
There was a TODO questioning whether breaking on >4bpp images
was the correct behaviour when RLE4 was detected. There is no
indication in the spec that RLE4 can be used with anything >4bpp,
so I believe this doesn't require additional follow-up.
MS Spec:
https://learn.microsoft.com/en-us/windows/win32/gdi/bitmap-compression
simple-vp8l-alpha-used-false.webp is a copy of simple-vp8l.webp,
with the byte at offset 0x18 changed from 0x10 to 0x00 -- that
is, the bit in the VP8L header that stores `is_alpha_used` is cleared.
We would already allocated a BGRx8888 instead of a BGRA8888 bitmap,
but keep actual alpha data in the `x` channel.
That lead to at least `image` still writing a PNG with an alpha channel.
So explicitly set the alpha channel to 0xff when is_alpha_used is false,
to make sure all consumers of decoded lossless webp data have behavior
consistent with other webp readers.
In practice, webp encoders usually don't write files that have
`is_alpha_used` set to false and then write actual alpha data to their
output. So this is rarely observable. However, for example for
lossy+ALPH webp files, the lossless webp used to store the ALPH channel
has `is_alpha_used` set to false and all channels but green are 0
(since the lossless green channel stores the alpha channel of a
lossy+ALPH webp). So if we dump such a bitmap to a standalone webp
file (e.g. with the temporary debugging code in fc3249a1ca),
then without this commit here, `image` would convert that webp to
a fully transparent webp, while other webp software would correctly
display the green image with opaque alpha.
