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weston/tests/alpha-blending-test.c

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/*
* Copyright 2020 Collabora, Ltd.
* Copyright 2021 Advanced Micro Devices, Inc.
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice (including the
* next paragraph) shall be included in all copies or substantial
* portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#include "config.h"
#include <math.h>
#include <stdio.h>
#include "weston-test-client-helper.h"
#include "weston-test-fixture-compositor.h"
#include "image-iter.h"
#include "color_util.h"
struct setup_args {
struct fixture_metadata meta;
enum renderer_type renderer;
bool color_management;
};
static const int ALPHA_STEPS = 256;
static const int BLOCK_WIDTH = 3;
static const struct setup_args my_setup_args[] = {
{
.renderer = RENDERER_PIXMAN,
.color_management = false,
.meta.name = "pixman"
},
{
.renderer = RENDERER_GL,
.color_management = false,
.meta.name = "GL"
},
{
.renderer = RENDERER_GL,
.color_management = true,
.meta.name = "GL sRGB EOTF"
},
};
static enum test_result_code
fixture_setup(struct weston_test_harness *harness, const struct setup_args *arg)
{
struct compositor_setup setup;
compositor_setup_defaults(&setup);
setup.renderer = arg->renderer;
setup.width = BLOCK_WIDTH * ALPHA_STEPS;
setup.height = 16;
setup.shell = SHELL_TEST_DESKTOP;
if (arg->color_management) {
weston_ini_setup(&setup,
cfgln("[core]"),
cfgln("color-management=true"));
}
return weston_test_harness_execute_as_client(harness, &setup);
}
DECLARE_FIXTURE_SETUP_WITH_ARG(fixture_setup, my_setup_args, meta);
static uint32_t
premult_color(uint32_t a, uint32_t r, uint32_t g, uint32_t b)
{
uint32_t c = 0;
c |= a << 24;
c |= (a * r / 255) << 16;
c |= (a * g / 255) << 8;
c |= a * b / 255;
return c;
}
static void
fill_alpha_pattern(struct buffer *buf)
{
struct image_header ih = image_header_from(buf->image);
int y;
assert(ih.pixman_format == PIXMAN_a8r8g8b8);
assert(ih.width == BLOCK_WIDTH * ALPHA_STEPS);
for (y = 0; y < ih.height; y++) {
uint32_t *row = image_header_get_row_u32(&ih, y);
uint32_t step;
for (step = 0; step < (uint32_t)ALPHA_STEPS; step++) {
uint32_t alpha = step * 255 / (ALPHA_STEPS - 1);
uint32_t color;
int i;
color = premult_color(alpha, 0, 255 - alpha, 255);
for (i = 0; i < BLOCK_WIDTH; i++)
*row++ = color;
}
}
}
enum blend_space {
BLEND_NONLINEAR,
BLEND_LINEAR,
};
static void
compare_sRGB_blend_a8r8g8b8(uint32_t bg32, uint32_t fg32, uint32_t dst32,
struct rgb_diff_stat *diffstat,
enum blend_space space)
{
struct color_float bg = a8r8g8b8_to_float(bg32);
struct color_float fg = a8r8g8b8_to_float(fg32);
struct color_float dst = a8r8g8b8_to_float(dst32);
struct color_float ref;
int i;
bg = color_float_unpremult(bg);
fg = color_float_unpremult(fg);
dst = color_float_unpremult(dst);
if (space == BLEND_LINEAR) {
sRGB_linearize(&bg);
sRGB_linearize(&fg);
}
for (i = 0; i < COLOR_CHAN_NUM; i++)
ref.rgb[i] = (1.0f - fg.a) * bg.rgb[i] + fg.a * fg.rgb[i];
if (space == BLEND_LINEAR)
sRGB_delinearize(&ref);
rgb_diff_stat_update(diffstat, &ref, &dst, &fg);
}
static uint8_t
red(uint32_t v)
{
return (v >> 16) & 0xff;
}
static uint8_t
blue(uint32_t v)
{
return v & 0xff;
}
static bool
pixels_monotonic(const uint32_t *row, int x)
{
bool ret = true;
if (red(row[x + 1]) > red(row[x])) {
testlog("pixel %d -> next: red value increases\n", x);
ret = false;
}
if (blue(row[x + 1]) < blue(row[x])) {
testlog("pixel %d -> next: blue value decreases\n", x);
ret = false;
}
return ret;
}
static void *
get_middle_row(struct buffer *buf)
{
struct image_header ih = image_header_from(buf->image);
assert(ih.width >= BLOCK_WIDTH * ALPHA_STEPS);
assert(ih.height >= BLOCK_WIDTH);
return image_header_get_row_u32(&ih, (BLOCK_WIDTH - 1) / 2);
}
static bool
check_blend_pattern(struct buffer *bg, struct buffer *fg, struct buffer *shot,
enum blend_space space)
{
FILE *dump = NULL;
#if 0
/*
* This file can be loaded in Octave for visualization. Find the script
* in tests/visualization/weston_plot_rgb_diff_stat.m and call it with
*
* weston_plot_rgb_diff_stat('alpha_blend-f01-dump.txt', 255, 8)
*/
dump = fopen_dump_file("dump");
#endif
/*
* Allow for +/- 1.5 code points of error in non-linear 8-bit channel
* value. This is necessary for the BLEND_LINEAR case.
*
* With llvmpipe, we could go as low as +/- 0.65 code points of error
* and still pass.
*
* AMD Polaris 11 would be ok with +/- 1.0 code points error threshold
* if not for one particular case of blending (a=254, r=0) into r=255,
* which results in error of 1.29 code points.
*/
const float tolerance = 1.5f / 255.f;
uint32_t *bg_row = get_middle_row(bg);
uint32_t *fg_row = get_middle_row(fg);
uint32_t *shot_row = get_middle_row(shot);
struct rgb_diff_stat diffstat = { .dump = dump, };
bool ret = true;
int x;
for (x = 0; x < BLOCK_WIDTH * ALPHA_STEPS - 1; x++) {
if (!pixels_monotonic(shot_row, x))
ret = false;
compare_sRGB_blend_a8r8g8b8(bg_row[x], fg_row[x], shot_row[x],
&diffstat, space);
}
if (diffstat.two_norm.max > tolerance)
ret = false;
rgb_diff_stat_print(&diffstat, __func__, 8);
if (dump)
fclose(dump);
return ret;
}
/*
* Test that alpha blending is roughly correct, and that an alpha ramp
* results in a strictly monotonic color ramp. This should ensure that any
* animation that varies alpha never goes "backwards" as that is easily
* noticeable.
*
* The background is a constant color. On top of that, there is an
* alpha-blended gradient with ramps in both alpha and color. Sub-surface
* ensures the correct positioning and stacking.
*
* The gradient consists of ALPHA_STEPS number of blocks. Block size is
* BLOCK_WIDTH x BLOCK_WIDTH and a block has a uniform color.
*
* In the blending result over x axis:
* - red goes from 1.0 to 0.0, monotonic
* - green is not monotonic
* - blue goes from 0.0 to 1.0, monotonic
*
* This test has two modes: BLEND_NONLINEAR and BLEND_LINEAR.
*
* BLEND_NONLINEAR does blending with pixel values as is, which are non-linear,
* and therefore result in "physically incorrect" blending result. Yet, people
* have accustomed to seeing this effect. This mode hits pipeline_premult()
* in fragment.glsl.
*
* BLEND_LINEAR has sRGB encoded pixels (non-linear). These are converted to
* linear light (optical) values, blended, and converted back to non-linear
* (electrical) values. This results in "physically more correct" blending
* result for some value of "physical". This mode hits pipeline_straight()
* in fragment.glsl, and tests even more things:
* - gl-renderer implementation of 1D LUT is correct
* - color-lcms instantiates the correct sRGB EOTF and inverse LUTs
* - color space conversions do not happen when both content and output are
* using their default color spaces
* - blending through gl-renderer shadow framebuffer
*/
TEST(alpha_blend)
{
const int width = BLOCK_WIDTH * ALPHA_STEPS;
const int height = BLOCK_WIDTH;
const pixman_color_t background_color = {
.red = 0xffff,
.green = 0x8080,
.blue = 0x0000,
.alpha = 0xffff
};
const struct setup_args *args;
struct client *client;
struct buffer *bg;
struct buffer *fg;
struct wl_subcompositor *subco;
struct wl_surface *surf;
struct wl_subsurface *sub;
struct buffer *shot;
bool match;
int seq_no;
enum blend_space space;
args = &my_setup_args[get_test_fixture_index()];
if (args->color_management) {
seq_no = 1;
space = BLEND_LINEAR;
} else {
seq_no = 0;
space = BLEND_NONLINEAR;
}
client = create_client();
subco = bind_to_singleton_global(client, &wl_subcompositor_interface, 1);
/* background window content */
bg = create_shm_buffer_a8r8g8b8(client, width, height);
fill_image_with_color(bg->image, &background_color);
/* background window, main surface */
client->surface = create_test_surface(client);
client->surface->width = width;
client->surface->height = height;
client->surface->buffer = bg; /* pass ownership */
surface_set_opaque_rect(client->surface,
&(struct rectangle){ 0, 0, width, height });
/* foreground blended content */
fg = create_shm_buffer_a8r8g8b8(client, width, height);
fill_alpha_pattern(fg);
/* foreground window, sub-surface */
surf = wl_compositor_create_surface(client->wl_compositor);
sub = wl_subcompositor_get_subsurface(subco, surf, client->surface->wl_surface);
/* sub-surface defaults to position 0, 0, top-most, synchronized */
wl_surface_attach(surf, fg->proxy, 0, 0);
wl_surface_damage(surf, 0, 0, width, height);
wl_surface_commit(surf);
/* attach, damage, commit background window */
move_client(client, 0, 0);
shot = capture_screenshot_of_output(client);
assert(shot);
match = verify_image(shot, "alpha_blend", seq_no, NULL, seq_no);
assert(check_blend_pattern(bg, fg, shot, space));
assert(match);
buffer_destroy(shot);
wl_subsurface_destroy(sub);
wl_surface_destroy(surf);
buffer_destroy(fg);
wl_subcompositor_destroy(subco);
client_destroy(client); /* destroys bg */
}