coreboot-kgpe-d16/payloads/libpayload
Julius Werner 7f87812c30 libpayload: cbgfx: Replace bilinear resampling with Lanczos
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 <jwerner@chromium.org>
Change-Id: Idde6f61865bfac2801ee4fff40ac64e4ebddff1a
Reviewed-on: https://review.coreboot.org/c/coreboot/+/42792
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Yu-Ping Wu <yupingso@google.com>
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
2020-07-09 00:32:17 +00:00
..
arch libpayload: arm64: silence libpayload main entry 2020-07-08 07:25:38 +00:00
bin treewide: Remove "this file is part of" lines 2020-05-11 17:11:40 +00:00
configs trogdor: add support for Bubs variant 2020-04-15 19:57:59 +00:00
crypto treewide: Remove "this file is part of" lines 2020-05-11 17:11:40 +00:00
curses treewide: Remove "this file is part of" lines 2020-05-11 17:11:40 +00:00
drivers libpayload: cbgfx: Replace bilinear resampling with Lanczos 2020-07-09 00:32:17 +00:00
gdb libpayload: gdb: Condition video console init on LP_VIDEO_CONSOLE 2020-06-22 12:24:42 +00:00
include libpayload: Add simple 32.32 fixed-point math API 2020-07-09 00:32:11 +00:00
libc libpayload: Add simple 32.32 fixed-point math API 2020-07-09 00:32:11 +00:00
libcbfs treewide: Remove "this file is part of" lines 2020-05-11 17:11:40 +00:00
liblz4 lz4: Fix out-of-bounds reads 2020-03-02 15:03:03 +00:00
liblzma treewide: Remove "this file is part of" lines 2020-05-11 17:11:40 +00:00
libpci treewide: Remove "this file is part of" lines 2020-05-11 17:11:40 +00:00
sample treewide: Remove "this file is part of" lines 2020-05-11 17:11:40 +00:00
tests
Doxyfile payloads: Remove/fix trailing whitespace 2018-09-04 12:38:40 +00:00
Kconfig libpayload: cbgfx: Replace bilinear resampling with Lanczos 2020-07-09 00:32:17 +00:00
LICENSES
LICENSE_GPL
Makefile treewide: Remove "this file is part of" lines 2020-05-11 17:11:40 +00:00
Makefile.inc treewide: Remove "this file is part of" lines 2020-05-11 17:11:40 +00:00
README payloads/libpayload: Update a Makefile for sample libpayload 2019-06-21 09:16:36 +00:00

README

-------------------------------------------------------------------------------
libpayload README
-------------------------------------------------------------------------------

libpayload is a minimal library to support standalone payloads
that can be booted with firmware like coreboot. It handles the setup
code, and provides common C library symbols such as malloc() and printf().

Note: This is _not_ a standard library for use with an operating system,
rather it's only useful for coreboot payload development!
See https://www.coreboot.org for details on coreboot.


Installation
------------

 $ git clone https://review.coreboot.org/coreboot.git

 $ cd coreboot/payloads/libpayload

 $ make menuconfig

 $ make

 $ make install (optional, will install into ./install per default)

On x86 systems, libpayload will always be 32-bit even if your host OS runs
in 64-bit, so you might have to install the 32-bit libgcc version.
On Debian systems you'd do 'apt-get install gcc-multilib' for example.

Run 'make distclean' before switching boards. This command will remove
your current .config file, so you need 'make menuconfig' again or
'make defconfig' in order to set up configuration. Default configuration
is based on 'configs/defconfig'. See the configs/ directory for examples
of configuration.


Usage
-----

Here's an example of a very simple payload (hello.c) and how to build it:

 #include <libpayload.h>

 int main(void)
 {
     printf("Hello, world!\n");
     return 0;
 }

Building the payload using the 'lpgcc' compiler wrapper:

 $ lpgcc -o hello.elf hello.c

Please see the sample/ directory for details.


Website and Mailing List
------------------------

The main website is https://www.coreboot.org/Libpayload.

For additional information, patches, and discussions, please join the
coreboot mailing list at https://www.coreboot.org/Mailinglist, where most
libpayload developers are subscribed.


Copyright and License
---------------------

See LICENSES.