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Updated documentation on memory usage

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Mirco Miranda
2026-05-29 07:56:33 +02:00
parent f450e5c9a9
commit a2a8c955df
2 changed files with 12 additions and 2 deletions
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12
README.md
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@@ -244,7 +244,7 @@ RGB.
Where possible, plugins support large images. By convention, many of the Where possible, plugins support large images. By convention, many of the
large image plugins are limited to a maximum of 300,000 x 300,000 pixels. large image plugins are limited to a maximum of 300,000 x 300,000 pixels.
Anyway, all plugins are also limited by the Anyway, all plugins are also limited by the
`QImageIOReader::allocationLimit()`. `QImageReader::allocationLimit()`.
> [!note] > [!note]
> You can change the maximum limit of 300000 pixels by setting the constant > You can change the maximum limit of 300000 pixels by setting the constant
@@ -300,8 +300,18 @@ consumption proportional to the size of the image to be saved.
Normally this is not a source of problems because the affected plugins Normally this is not a source of problems because the affected plugins
are limited to maximum images of 2GiB or less. are limited to maximum images of 2GiB or less.
Note that the value of `QImageReader::allocationLimit()` is only used when
allocating a new `QImage`. Since this parameter was created to limit damage
caused by corrupted files, any conversion of `QImage` (for example, with
`QImage::convertTo()`) is not subject to this limit.
On plugins for formats that support large images, progressive conversion has On plugins for formats that support large images, progressive conversion has
been used or the maximum size of the image that can be saved has been limited. been used or the maximum size of the image that can be saved has been limited.
Plugins that use external libraries don't always allow progressive decoding
(e.g., the JPEG series). In these cases, the memory required for reading
may be much larger than the entire decoded image. When the external library has
a maximum memory limit function, the value of `QImageReader::allocationLimit()`
is set.
### Non-RGB formats ### Non-RGB formats

2
autotests/ossfuzz/kimgio_fuzzer.cc
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@@ -63,7 +63,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
int argc = 0; int argc = 0;
QCoreApplication a(argc, nullptr); QCoreApplication a(argc, nullptr);
QImageReader::setAllocationLimit(2000); QImageReader::setAllocationLimit(512);
QImageIOHandler* handler = new HANDLER(); QImageIOHandler* handler = new HANDLER();