This fixes an issue where GIF images without a global color table would
have the first segment incorrectly interpreted as color table data.
Makes many more screenshots appear on https://virtuallyfun.com/ :^)
TIFF files are made in a way that make them easily extendable and over
the years people have made sure to exploit that. In other words, it's
easy to find images with non-standard tags. Instead of returning an
error for that, let's skip them.
Note that we need to make sure to realign the reading head in the file.
The test case was originally a 10x10 checkerboard image with required
tags, and also the `DocumentName` tag. Then, I modified this tag in a
hexadecimal editor and replaced its id with 30 000 (0x3075 as a LE u16)
and the type with the same value as well. This is AFAIK, never used as
a custom TIFF tag, so this should remain an invalid tag id and type.
For solid color fills (with alpha = 255), the rasterizer now tracks
spans of solid colors within a scanline and fills the entire span with
a single call to fast_u32_fill().
This gave up to a 1.5x speedup drawing the Ghostscript Tiger within
SerenityOS.
In XYZ space, gray doesn't have three equal values. Instead, it is
a line through the whitepoint.
(Multiplying by the whitepoint has the same effect as multiplying
the sRGB matrix with a (g, g, g) vector, since the numbers on
the matrix's rows add up to the whitepoint.)
Fixes the very slight red tint on all the figures in chapter 4
of the PDF 1.7 spec.
We were previously only checking the first value, this is wrong for tags
that accept multiple values (e.g. ExtraSamples) and can lead to crashes
on malformed images containing tags with a count of 0.
The TIFF spec is constructed in a way that many tags are defined in
multiple places but some of these definitions are partial. If we look
into "Section 8: Baseline Field Reference Guide", we can see that these
tags indeed have an enforced length of 1.
With this change, instead of applying scroll offsets during the
recording of the painting command list, we do the following:
1. Collect all boxes with scrollable overflow into a PaintContext,
each with an id and the total amount of scrolling offset accumulated
from ancestor scrollable boxes.
2. During the recording phase assign a corresponding scroll_frame_id to
each command that paints content within a scrollable box.
3. Before executing the recorded commands, translate each command that
has a scroll_frame_id by the accumulated scroll offset.
This approach has following advantages:
- Implementing nested scrollables becomes much simpler, as the
recording phase only requires the correct assignment of the nearest
scrollable's scroll_frame_id, while the accumulated offset from
ancestors is applied subsequently.
- The recording of painting commands is not tied to a specific offset
within scrollable boxes, which means in the future, it will be
possible to update the scrolling offset and repaint without the need
to re-record painting commands.
The decoder assumes that k's sampling factor matches y's at the moment.
Better to error out than to silently render something broken.
For ycck, covered by ycck-2111.jpg in the tests.
We currently assume that the K (black) channel uses the same sampling
as the Y channel already, so this already works as long as we don't
error out on it.
Before this change, we would only cache and reuse Gfx::ScaledFont
instances for downloaded CSS fonts.
By moving it into Gfx::VectorFont, we get caching for all vector fonts,
including local system TTFs etc.
This avoids a *lot* of style invalidations in LibWeb, since we now vend
the same Gfx::Font pointer for the same font when used repeatedly.
This avoids doing pointless plotting for scanlines that will never be
seen.
Note: This currently can only clip edges vertically. Horizontal clipping
is more tricky, since edges that are not visible can still change how
things accumulate across the scanline.
Fixes#22382
Sadly, this causes a bunch of LibWeb test churn as this change
imperceptibly changes the final rasterized output.
This allows us to reject invalid images before trying to decode them.
The spec requires more tag to be present[1] but as we don't use them for
decoding I don't see the point.
[1] - XResolution, YResolution and ResolutionUnit
TIFF images with the PhotometricInterpretation tag set to RGBPalette are
based on indexed colors instead of explicitly describing the color for
each pixel. Let's add support for them.
The test case was generated with GIMP using the Indexed image mode after
adding an alpha layer. Not all decoders are able to open this image, but
GIMP can.
In a bunch of cases, this actually ends up simplifying the code as
to_number will handle something such as:
```
Optional<I> opt;
if constexpr (IsSigned<I>)
opt = view.to_int<I>();
else
opt = view.to_uint<I>();
```
For us.
The main goal here however is to have a single generic number conversion
API between all of the String classes.
UnassociatedAlpha is the one used by GIMP when generating TIFF images
with transparency. Support is added for Grayscale and RGB images as it's
the two that we support right now but managing transparency should be
really straightforward for other types as well.
As per the specification, TIFF readers should gracefully skip samples
that they are not able to interpret.
This patch allow us to read `strike.tif` from the libtiff test suite as
an RGB image.
The number of samples is not a good measure to deduce the type of image
we are decoding. As per the TIFF spec, the PhotometricInterpretation tag
is required and we should use that instead.
This changes the splitting to use a stack, which ensures the resulting
line segments follow the path in order. This will be important for SVG
`<textPath>`s which place text along a path.
This compression (tag Compression=2) is not very popular on its own, but
a base to implement CCITT3 2D and CCITT4 compressions.
As the format has no real benefits, it is quite hard to find an app that
accepts tho encode that for you. So I used the following program that
calls `libtiff` directly:
```cpp
#include <vector>
#include <cstdlib>
#include <iostream>
#include <tiffio.h>
// An array containing 0 and 1 of length width * height.
extern std::vector<uint8_t> array;
int main() {
// From: https://stackoverflow.com/a/34257789
TIFF *image = TIFFOpen("input.tif", "w");
int const width = 400;
int const height = 300;
TIFFSetField(image, TIFFTAG_IMAGEWIDTH, width);
TIFFSetField(image, TIFFTAG_IMAGELENGTH, height);
TIFFSetField(image, TIFFTAG_PHOTOMETRIC, 0);
TIFFSetField(image, TIFFTAG_COMPRESSION, COMPRESSION_CCITTRLE);
TIFFSetField(image, TIFFTAG_BITSPERSAMPLE, 1);
TIFFSetField(image, TIFFTAG_SAMPLESPERPIXEL, 1);
TIFFSetField(image, TIFFTAG_ROWSPERSTRIP, 1);
std::vector<uint8_t> scan_line(width / 8 + 8, 0);
int count = 0;
for (int i = 0; i < height; i++) {
std::fill(scan_line.begin(), scan_line.end(), 0);
for (int x = 0; x < width; ++x) {
uint8_t eight_pixels = scan_line.at(x / 8);
eight_pixels = eight_pixels << 1;
eight_pixels |= !array.at(i * width + x);
scan_line.at(x / 8) = eight_pixels;
}
int bytes = int(width / 8.0 + 0.5);
if (TIFFWriteScanline(image, scan_line.data(), i, bytes) != 1)
std::cerr << "Something went wrong\n";
}
TIFFClose(image);
}
```
As pointed out by @nico, while doing a right-shift to downscale is fine,
a left-shift to upscale gives wrong results. As an example, imagine a 2-
bits value containing 3, left-shifting it would give 192 instead of 255.
These tags are either part of the baseline specification or included by
default by GIMP when exporting TIFF files. Note that we don't add
support for them in the decoder yet. This commit only allows us to parse
the metadata and display it gracefully.
This commit un-deprecates DeprecatedString, and repurposes it as a byte
string.
As the null state has already been removed, there are no other
particularly hairy blockers in repurposing this type as a byte string
(what it _really_ is).
This commit is auto-generated:
$ xs=$(ack -l \bDeprecatedString\b\|deprecated_string AK Userland \
Meta Ports Ladybird Tests Kernel)
$ perl -pie 's/\bDeprecatedString\b/ByteString/g;
s/deprecated_string/byte_string/g' $xs
$ clang-format --style=file -i \
$(git diff --name-only | grep \.cpp\|\.h)
$ gn format $(git ls-files '*.gn' '*.gni')
According to the CSS font matching algorithm specification, it is
supposed to be executed for each glyph instead of each text run, as is
currently done. This change partially implements this by having the
font matching algorithm produce a list of fonts against which each
glyph will be tested to find its suitable font.
Now, it becomes possible to have per-glyph fallback fonts: if the
needed glyph is not present in a font, we can check the subsequent
fonts in the list.
RepeatingBitmapPaintStyle tiles a bitmap passed on passed in parameters
and paints according to that.
OffsetPaintStyle offsets an existing paint style and paints with that.
These two will be useful in the PDF renderer.
