This patch improves the image resampling (scaling) code in CBGFX to use the Lanczos algorithm that is widely considered the "best" resampling algorithm (e.g. also the first choice in Python's PIL library). It is of course much more elaborate and therefore slower than bilinear resampling, but a lot of the difference can be made up with optimizations, and the resulting code was found to still produce acceptable speeds for existing Chrome OS UI use cases (on an Arm Cortex-A55 device, time to scale an image to 1101x593 went from ~88ms to ~275ms, a little over 3x slowdown). Nevertheless, if this should be too slow for anyone there's also an option to tune it down a little, but still much better than bilinear (same operation was ~170ms with this). Example images (scaled up by a factor of 7): Old (bilinear): https://i.imgur.com/ytr2n4Z.png New (Lanczos a=3): https://i.imgur.com/f0vKluM.png Signed-off-by: Julius Werner <email@example.com> Change-Id: Idde6f61865bfac2801ee4fff40ac64e4ebddff1a Reviewed-on: https://review.coreboot.org/c/coreboot/+/42792 Tested-by: build bot (Jenkins) <firstname.lastname@example.org> Reviewed-by: Yu-Ping Wu <email@example.com> Reviewed-by: Hung-Te Lin <firstname.lastname@example.org>
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coreboot is a Free Software project aimed at replacing the proprietary BIOS
(firmware) found in most computers. coreboot performs a little bit of
hardware initialization and then executes additional boot logic, called a
With the separation of hardware initialization and later boot logic,
coreboot can scale from specialized applications that run directly
firmware, run operating systems in flash, load custom
bootloaders, or implement firmware standards, like PC BIOS services or
UEFI. This allows for systems to only include the features necessary
in the target application, reducing the amount of code and flash space
coreboot was formerly known as LinuxBIOS.
After the basic initialization of the hardware has been performed, any
desired “payload” can be started by coreboot.
See https://www.coreboot.org/Payloads for a list of supported payloads.
coreboot supports a wide range of chipsets, devices, and mainboards.
For details please consult:
ANY_TOOLCHAINKconfig option if you’re feeling lucky (no support in this
Please consult https://www.coreboot.org/Build_HOWTO for details.
If you want to test coreboot without any risks before you really decide
to use it on your hardware, you can use the QEMU system emulator to run
coreboot virtually in QEMU.
Please see https://www.coreboot.org/QEMU for details.
Further details on the project, a FAQ, many HOWTOs, news, development
guidelines and more can be found on the coreboot website:
You can contact us directly on the coreboot mailing list:
The copyright on coreboot is owned by quite a large number of individual
developers and companies. Please check the individual source files for details.
coreboot is licensed under the terms of the GNU General Public License (GPL).
Some files are licensed under the “GPL (version 2, or any later version)",
and some files are licensed under the “GPL, version 2”. For some parts, which
were derived from other projects, other (GPL-compatible) licenses may apply.
Please check the individual source files for details.
This makes the resulting coreboot images licensed under the GPL, version 2.