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tests: lib: pixel: add unit tests for format conversion
The tests use data generated by the ffmpeg command line utilty in order to avoid bias by having the same person implementing the tests and the source code. Signed-off-by: Josuah Demangeon <me@josuah.net>
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‎tests/lib/pixel/CMakeLists.txt

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# SPDX-License-Identifier: Apache-2.0
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cmake_minimum_required(VERSION 3.20.0)
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find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
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project(pixel)
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FILE(GLOB app_sources src/*.c)
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target_sources(app PRIVATE ${app_sources})

‎tests/lib/pixel/prj.conf

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CONFIG_PIXEL_LOG_LEVEL_DBG=y
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CONFIG_ZTEST=y
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CONFIG_PIXEL=y

‎tests/lib/pixel/src/pixel_format.c

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/*
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* Copyright (c) 2025 tinyVision.ai Inc.
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <zephyr/kernel.h>
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#include <zephyr/random/random.h>
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#include <zephyr/ztest.h>
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#include <zephyr/pixel/formats.h>
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#include <zephyr/pixel/print.h>
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#define WIDTH 16
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#define HEIGHT 16
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#define ERROR_MARGIN 10
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/*
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* To get YUV BT.709 test data:
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*
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* ffmpeg -y -f lavfi -colorspace bt709 -i color=#rrggbb:2x2:d=3,format=rgb24 \
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* -f rawvideo -pix_fmt yuyv422 - | hexdump -C
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*
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* To get RGB565 test data:
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*
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* ffmpeg -y -f lavfi -i color=$rgb:2x2:d=3,format=rgb24 \
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* -f rawvideo -pix_fmt rgb565 - | hexdump -C
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*/
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const struct color_ref {
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uint8_t rgb24[3];
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uint8_t rgb565[2];
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uint8_t rgb332[1];
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uint8_t yuv24_bt709[3];
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uint8_t yuv24_bt601[3];
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} reference_data[] = {
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/* Primary colors */
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{{0x00, 0x00, 0x00}, {0x00, 0x00}, {0x00}, {0x10, 0x80, 0x80}, {0x10, 0x80, 0x80}},
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{{0x00, 0x00, 0xff}, {0x00, 0x1f}, {0x03}, {0x20, 0xf0, 0x76}, {0x29, 0xf1, 0x6e}},
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{{0x00, 0xff, 0x00}, {0x07, 0xe0}, {0x1c}, {0xad, 0x2a, 0x1a}, {0x9a, 0x2a, 0x35}},
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{{0x00, 0xff, 0xff}, {0x07, 0xff}, {0x1f}, {0xbc, 0x9a, 0x10}, {0xb4, 0xa0, 0x23}},
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{{0xff, 0x00, 0x00}, {0xf8, 0x00}, {0xe0}, {0x3f, 0x66, 0xf0}, {0x50, 0x5b, 0xee}},
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{{0xff, 0x00, 0xff}, {0xf8, 0x1f}, {0xe3}, {0x4e, 0xd6, 0xe6}, {0x69, 0xcb, 0xdc}},
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{{0xff, 0xff, 0x00}, {0xff, 0xe0}, {0xfc}, {0xdb, 0x10, 0x8a}, {0xd0, 0x0a, 0x93}},
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{{0xff, 0xff, 0xff}, {0xff, 0xff}, {0xff}, {0xeb, 0x80, 0x80}, {0xeb, 0x80, 0x80}},
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/* Arbitrary colors */
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{{0x00, 0x70, 0xc5}, {0x03, 0x98}, {0x0f}, {0x61, 0xb1, 0x4b}, {0x5e, 0xb5, 0x4d}},
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{{0x33, 0x8d, 0xd1}, {0x3c, 0x7a}, {0x33}, {0x7d, 0xa7, 0x56}, {0x7b, 0xab, 0x57}},
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{{0x66, 0xa9, 0xdc}, {0x6d, 0x5b}, {0x77}, {0x98, 0x9d, 0x61}, {0x96, 0xa0, 0x61}},
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{{0x7d, 0xd2, 0xf7}, {0x86, 0x9e}, {0x7b}, {0xb7, 0x99, 0x59}, {0xb3, 0x9d, 0x5a}},
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{{0x97, 0xdb, 0xf9}, {0x9e, 0xde}, {0x9b}, {0xc2, 0x94, 0x61}, {0xbf, 0x97, 0x62}},
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{{0xb1, 0xe4, 0xfa}, {0xb7, 0x3f}, {0xbf}, {0xcc, 0x8f, 0x69}, {0xca, 0x91, 0x69}},
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{{0x79, 0x29, 0xd2}, {0x79, 0x5a}, {0x67}, {0x4c, 0xc2, 0x9c}, {0x57, 0xbf, 0x96}},
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{{0x94, 0x54, 0xdb}, {0x9a, 0xbb}, {0x8b}, {0x6c, 0xb5, 0x97}, {0x75, 0xb3, 0x92}},
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{{0xaf, 0x7f, 0xe4}, {0xb3, 0xfc}, {0xaf}, {0x8c, 0xa8, 0x91}, {0x93, 0xa6, 0x8d}},
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};
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static uint8_t line_in[WIDTH * 4];
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static uint8_t line_out[WIDTH * 4];
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void test_conversion(const uint8_t *pix_in, size_t pix_in_size, size_t pix_in_step,
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const uint8_t *pix_out, size_t pix_out_size, size_t pix_out_step,
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void (*fn)(const uint8_t *in, uint8_t *out, uint16_t width))
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{
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bool done = false;
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/* Fill the input line as much as possible */
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for (size_t w = 0; w < WIDTH; w += pix_in_step) {
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memcpy(&line_in[w * pix_in_size], pix_in, pix_in_size * pix_in_step);
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}
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/* Perform the conversion to test */
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fn(line_in, line_out, WIDTH);
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printf("out:");
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for (int i = 0; i < pix_out_step * pix_out_size; i++) {
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printf(" %02x", line_out[i]);
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}
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printf("\n");
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printf("ref:");
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for (int i = 0; i < pix_out_step * pix_out_size; i++) {
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printf(" %02x", pix_out[i]);
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}
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printf("\n");
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/* Scan the result against the reference output pixel to make sure it worked */
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for (size_t w = 0; w < WIDTH; w += pix_out_step) {
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for (int i = 0; w * pix_out_size + i < (w + pix_out_step) * pix_out_size; i++) {
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zassert_within(line_out[w * pix_out_size + i], pix_out[i], 9,
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"at %u: value 0x%02x, reference 0x%02x",
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i, line_out[w * pix_out_size + i], pix_out[i]);
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}
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/* Make sure we visited that loop */
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done = true;
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}
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zassert_true(done);
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}
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ZTEST(lib_pixel_format, test_pixel_format_line)
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{
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for (size_t i = 0; i < ARRAY_SIZE(reference_data); i++) {
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/* The current color we are testing */
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const struct color_ref *ref = &reference_data[i];
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/* Generate very small buffers out of the reference tables */
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const uint8_t rgb24[] = {
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ref->rgb24[0],
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ref->rgb24[1],
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ref->rgb24[2],
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};
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const uint8_t rgb565be[] = {
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ref->rgb565[0],
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ref->rgb565[1],
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};
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const uint8_t rgb565le[] = {
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ref->rgb565[1],
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ref->rgb565[0],
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};
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const uint8_t rgb332[] = {
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ref->rgb332[0],
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};
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const uint8_t yuyv_bt709[] = {
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ref->yuv24_bt709[0],
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ref->yuv24_bt709[1],
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ref->yuv24_bt709[0],
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ref->yuv24_bt709[2],
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};
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printf("\ncolor #%02x%02x%02x\n", ref->rgb24[0], ref->rgb24[1], ref->rgb24[2]);
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test_conversion(rgb24, 3, 1, rgb565be, 2, 1, &pixel_rgb24line_to_rgb565beline);
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printf("rgb24 in |");
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pixel_print_rgb24frame_truecolor(line_in, sizeof(line_in), WIDTH / 2, 2);
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printf("rgb565 out|");
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pixel_print_rgb565beframe_truecolor(line_out, sizeof(line_out), WIDTH / 2, 2);
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test_conversion(rgb24, 3, 1, rgb565le, 2, 1, &pixel_rgb24line_to_rgb565leline);
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printf("rgb24 in |");
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pixel_print_rgb24frame_truecolor(line_in, sizeof(line_in), WIDTH / 2, 2);
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printf("rgb565 out|");
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pixel_print_rgb565leframe_truecolor(line_out, sizeof(line_out), WIDTH / 2, 2);
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test_conversion(rgb24, 3, 1, rgb332, 1, 1, &pixel_rgb24line_to_rgb332line);
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printf("rgb24 in |");
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pixel_print_rgb24frame_truecolor(line_in, sizeof(line_in), WIDTH / 2, 2);
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printf("rgb332 out|");
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pixel_print_rgb332frame_truecolor(line_out, sizeof(line_out), WIDTH / 2, 2);
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test_conversion(rgb565be, 2, 1, rgb24, 3, 1, &pixel_rgb565beline_to_rgb24line);
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printf("rgb565 in |");
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pixel_print_rgb565beframe_truecolor(line_in, sizeof(line_in), WIDTH / 2, 2);
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printf("rgb24 out |");
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pixel_print_rgb24frame_truecolor(line_out, sizeof(line_out), WIDTH / 2, 2);
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test_conversion(rgb565le, 2, 1, rgb24, 3, 1, &pixel_rgb565leline_to_rgb24line);
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printf("rgb565 in |");
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pixel_print_rgb565leframe_truecolor(line_in, sizeof(line_in), WIDTH / 2, 2);
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printf("rgb24 out |");
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pixel_print_rgb24frame_truecolor(line_out, sizeof(line_out), WIDTH / 2, 2);
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test_conversion(rgb24, 3, 1, yuyv_bt709, 2, 2, &pixel_rgb24line_to_yuyvline_bt709);
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printf("rgb24 in |");
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pixel_print_rgb24frame_truecolor(line_in, sizeof(line_in), WIDTH / 2, 2);
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printf("bt709 out |");
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pixel_print_yuyvframe_bt709_truecolor(line_out, sizeof(line_out), WIDTH / 2, 2);
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test_conversion(yuyv_bt709, 2, 2, rgb24, 3, 1, &pixel_yuyvline_to_rgb24line_bt709);
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printf("bt709 in |");
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pixel_print_yuyvframe_bt709_truecolor(line_in, sizeof(line_in), WIDTH / 2, 2);
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printf("rgb24 out |");
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pixel_print_rgb24frame_truecolor(line_out, sizeof(line_out), WIDTH / 2, 2);
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}
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}
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/* From RGB24 */
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static PIXEL_RGB24STREAM_TO_RGB565BESTREAM(step_rgb24_to_rgb565be, WIDTH, HEIGHT);
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static PIXEL_RGB24STREAM_TO_RGB565LESTREAM(step_rgb24_to_rgb565le, WIDTH, HEIGHT);
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static PIXEL_RGB24STREAM_TO_YUYVSTREAM_BT709(step_rgb24_to_yuyv, WIDTH, HEIGHT);
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/* To RGB24 */
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static PIXEL_RGB565BESTREAM_TO_RGB24STREAM(step_rgb565be_to_rgb24, WIDTH, HEIGHT);
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static PIXEL_RGB565LESTREAM_TO_RGB24STREAM(step_rgb565le_to_rgb24, WIDTH, HEIGHT);
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static PIXEL_YUYVSTREAM_TO_RGB24STREAM_BT709(step_yuyv_to_rgb24, WIDTH, HEIGHT);
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static uint8_t rgb24frame_in[WIDTH * HEIGHT * 3];
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static uint8_t rgb24frame_out[WIDTH * HEIGHT * 3];
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ZTEST(lib_pixel_format, test_pixel_format_stream)
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{
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struct pixel_stream root = {0};
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struct pixel_stream *step = &root;
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struct pixel_stream step_export = {
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.ring = RING_BUF_INIT(rgb24frame_out, sizeof(rgb24frame_out)),
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.pitch = WIDTH * 3,
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.height = HEIGHT,
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.name = "[export]",
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};
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/* Generate test input data */
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for (size_t i = 0; i < sizeof(rgb24frame_in); i++) {
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rgb24frame_in[i] = i / 3;
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}
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/* Build and run the pipeline */
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step = step->next = &step_rgb24_to_rgb565le;
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step = step->next = &step_rgb565le_to_rgb24;
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step = step->next = &step_rgb24_to_rgb565be;
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step = step->next = &step_rgb565be_to_rgb24;
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step = step->next = &step_rgb24_to_yuyv;
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step = step->next = &step_yuyv_to_rgb24;
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step = step->next = &step_export;
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pixel_stream_load(root.next, rgb24frame_in, sizeof(rgb24frame_in));
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printf("input:\n");
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pixel_print_rgb24frame_truecolor(rgb24frame_in, sizeof(rgb24frame_in), WIDTH, HEIGHT);
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printf("output:\n");
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pixel_print_rgb24frame_truecolor(rgb24frame_out, sizeof(rgb24frame_out), WIDTH, HEIGHT);
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for (int i = 0; i < sizeof(rgb24frame_out); i++) {
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/* Precision is not 100% as some conversions steps are lossy */
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zassert_within(rgb24frame_in[i], rgb24frame_out[i], ERROR_MARGIN,
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"Testing position %u", i);
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}
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}
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ZTEST_SUITE(lib_pixel_format, NULL, NULL, NULL, NULL, NULL);

‎tests/lib/pixel/src/pixel_resize.c

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/*
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* Copyright (c) 2025 tinyVision.ai Inc.
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <zephyr/kernel.h>
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#include <zephyr/random/random.h>
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#include <zephyr/ztest.h>
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#include <zephyr/pixel/resize.h>
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#include <zephyr/pixel/formats.h>
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#include <zephyr/pixel/print.h>
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#define WIDTH_IN 32
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#define HEIGHT_IN 16
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#define PITCH_IN (WIDTH_IN * 3)
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#define WIDTH_OUT 24
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#define HEIGHT_OUT 24
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#define PITCH_OUT (WIDTH_OUT * 3)
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#define ERROR_MARGIN 9
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/* Input/output buffers */
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static uint8_t rgb24frame_in[WIDTH_IN * HEIGHT_IN * 3];
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static uint8_t rgb24frame_out[WIDTH_OUT * HEIGHT_OUT * 3];
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/* Stream conversion steps */
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static PIXEL_RGB24STREAM_TO_RGB565BESTREAM(step_rgb24_to_rgb565be, WIDTH_IN, HEIGHT_IN);
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static PIXEL_RGB24STREAM_TO_RGB565LESTREAM(step_rgb24_to_rgb565le, WIDTH_IN, HEIGHT_IN);
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static PIXEL_RGB565BESTREAM_TO_RGB24STREAM(step_rgb565be_to_rgb24, WIDTH_OUT, HEIGHT_OUT);
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static PIXEL_RGB565LESTREAM_TO_RGB24STREAM(step_rgb565le_to_rgb24, WIDTH_OUT, HEIGHT_OUT);
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static PIXEL_SUBSAMPLE_RGB24STREAM(step_subsample_rgb24, WIDTH_IN, HEIGHT_IN);
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static PIXEL_SUBSAMPLE_RGB565STREAM(step_subsample_rgb565, WIDTH_IN, HEIGHT_IN);
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struct pixel_stream root = {0};
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static void test_resize(void)
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{
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/* Run the pipeline */
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pixel_stream_load(root.next, rgb24frame_in, sizeof(rgb24frame_in));
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printf("input:\n");
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pixel_print_rgb24frame_truecolor(rgb24frame_in, sizeof(rgb24frame_in), WIDTH_IN, HEIGHT_IN);
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printf("output:\n");
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pixel_print_rgb24frame_truecolor(rgb24frame_out, sizeof(rgb24frame_out), WIDTH_OUT,
47+
HEIGHT_OUT);
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size_t w = WIDTH_OUT;
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size_t h = HEIGHT_OUT;
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size_t p = PITCH_OUT;
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/* Test top left quadramt */
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zassert_within(rgb24frame_out[(0) * p + (0) * 3 + 0], 0x00, ERROR_MARGIN);
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zassert_within(rgb24frame_out[(0) * p + (0) * 3 + 1], 0x00, ERROR_MARGIN);
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zassert_within(rgb24frame_out[(0) * p + (0) * 3 + 2], 0x7f, ERROR_MARGIN);
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zassert_within(rgb24frame_out[(h / 2 - 1) * p + (w / 2 - 1) * 3 + 0], 0x00, ERROR_MARGIN);
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zassert_within(rgb24frame_out[(h / 2 - 1) * p + (w / 2 - 1) * 3 + 1], 0x00, ERROR_MARGIN);
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zassert_within(rgb24frame_out[(h / 2 - 1) * p + (w / 2 - 1) * 3 + 2], 0x7f, ERROR_MARGIN);
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/* Test bottom left quadrant */
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zassert_within(rgb24frame_out[(h - 1) * p + (0) * 3 + 0], 0x00, ERROR_MARGIN);
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zassert_within(rgb24frame_out[(h - 1) * p + (0) * 3 + 1], 0xff, ERROR_MARGIN);
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zassert_within(rgb24frame_out[(h - 1) * p + (0) * 3 + 2], 0x7f, ERROR_MARGIN);
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zassert_within(rgb24frame_out[(h / 2 + 1) * p + (w / 2 - 1) * 3 + 0], 0x00, ERROR_MARGIN);
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zassert_within(rgb24frame_out[(h / 2 + 1) * p + (w / 2 - 1) * 3 + 1], 0xff, ERROR_MARGIN);
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zassert_within(rgb24frame_out[(h / 2 + 1) * p + (w / 2 - 1) * 3 + 2], 0x7f, ERROR_MARGIN);
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/* Test top right quadrant */
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zassert_within(rgb24frame_out[(0) * p + (w - 1) * 3 + 0], 0xff, ERROR_MARGIN);
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zassert_within(rgb24frame_out[(0) * p + (w - 1) * 3 + 1], 0x00, ERROR_MARGIN);
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zassert_within(rgb24frame_out[(0) * p + (w - 1) * 3 + 2], 0x7f, ERROR_MARGIN);
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zassert_within(rgb24frame_out[(h / 2 - 1) * p + (w / 2 + 1) * 3 + 0], 0xff, ERROR_MARGIN);
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zassert_within(rgb24frame_out[(h / 2 - 1) * p + (w / 2 + 1) * 3 + 1], 0x00, ERROR_MARGIN);
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zassert_within(rgb24frame_out[(h / 2 - 1) * p + (w / 2 + 1) * 3 + 2], 0x7f, ERROR_MARGIN);
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/* Test bottom right quadrant */
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zassert_within(rgb24frame_out[(h - 1) * p + (w - 1) * 3 + 0], 0xff, ERROR_MARGIN);
79+
zassert_within(rgb24frame_out[(h - 1) * p + (w - 1) * 3 + 1], 0xff, ERROR_MARGIN);
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zassert_within(rgb24frame_out[(h - 1) * p + (w - 1) * 3 + 2], 0x7f, ERROR_MARGIN);
81+
zassert_within(rgb24frame_out[(h / 2 + 1) * p + (w / 2 + 1) * 3 + 0], 0xff, ERROR_MARGIN);
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zassert_within(rgb24frame_out[(h / 2 + 1) * p + (w / 2 + 1) * 3 + 1], 0xff, ERROR_MARGIN);
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zassert_within(rgb24frame_out[(h / 2 + 1) * p + (w / 2 + 1) * 3 + 2], 0x7f, ERROR_MARGIN);
84+
}
85+
86+
ZTEST(lib_pixel_resize, test_pixel_resize_stream)
87+
{
88+
struct pixel_stream step_export_rgb24 = {
89+
.ring = RING_BUF_INIT(rgb24frame_out, sizeof(rgb24frame_out)),
90+
.pitch = WIDTH_OUT * 3,
91+
.width = WIDTH_OUT,
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.height = HEIGHT_OUT,
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.name = "[export]",
94+
};
95+
struct pixel_stream *step;
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/* Generate test input data */
98+
for (uint16_t h = 0; h <= HEIGHT_IN; h++) {
99+
for (uint16_t w = 0; w < WIDTH_IN; w++) {
100+
rgb24frame_in[h * PITCH_IN + w * 3 + 0] = w < WIDTH_IN / 2 ? 0x00 : 0xff;
101+
rgb24frame_in[h * PITCH_IN + w * 3 + 1] = h < HEIGHT_IN / 2 ? 0x00 : 0xff;
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rgb24frame_in[h * PITCH_IN + w * 3 + 2] = 0x7f;
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}
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}
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/* RGB24 */
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step = &root;
108+
step = step->next = &step_subsample_rgb24;
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step = step->next = &step_export_rgb24;
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test_resize();
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pixel_stream_get_all_input(&step_export_rgb24);
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/* RGB565LE */
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step = &root;
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step = step->next = &step_rgb24_to_rgb565le;
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step = step->next = &step_subsample_rgb565;
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step = step->next = &step_rgb565le_to_rgb24;
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step = step->next = &step_export_rgb24;
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test_resize();
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pixel_stream_get_all_input(&step_export_rgb24);
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/* RGB565BE */
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step = &root;
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step = step->next = &step_rgb24_to_rgb565be;
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step = step->next = &step_subsample_rgb565;
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step = step->next = &step_rgb565be_to_rgb24;
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step = step->next = &step_export_rgb24;
128+
test_resize();
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pixel_stream_get_all_input(&step_export_rgb24);
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}
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ZTEST_SUITE(lib_pixel_resize, NULL, NULL, NULL, NULL, NULL);

‎tests/lib/pixel/testcase.yaml

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tests:
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libraries.pixel:
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tags:
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- pixel
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integration_platforms:
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- qemu_cortex_m3
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- native_sim

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