From 25a4bb5327a8058e20c0466c5d6673523945b9fa Mon Sep 17 00:00:00 2001
From: Pekka Paalanen <pekka.paalanen@collabora.com>
Date: Fri, 12 Mar 2021 14:06:34 +0200
Subject: [PATCH] gl-renderer: add shader bit input_is_premult
Add a new shader requirements bit input_is_premult which says whether
the texture sampling results in premultiplied alpha or not. Currently
this can be deduced fully from the shader texture variant, but in the
future there might a protocol extension to explicitly control it. Hence
the need for a new bit.
yuva2rgba() is changed to produce straight alpha always. This makes
sample_input_texture() sometimes produce straight or premultiplied
alpha. The input_is_premult bit needs to match sample_input_texture()
behavior. Doing this should save three multiplications in the shader for
straight alpha formats.
pipeline_premult() function is added, because in the future another
pipeline working on straight alpha will be needed.
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>
---
libweston/renderer-gl/fragment.glsl | 23 ++++++++++++++----
libweston/renderer-gl/gl-renderer-internal.h | 6 ++++-
libweston/renderer-gl/gl-renderer.c | 6 +++++
libweston/renderer-gl/gl-shaders.c | 25 +++++++++++++++++++-
4 files changed, 54 insertions(+), 6 deletions(-)
diff --git a/libweston/renderer-gl/fragment.glsl b/libweston/renderer-gl/fragment.glsl
index f56d1bc1f9..b5143edce4 100644
--- a/libweston/renderer-gl/fragment.glsl
+++ b/libweston/renderer-gl/fragment.glsl
@@ -53,6 +53,7 @@ precision mediump float;
* snippet.
*/
compile_const int c_variant = DEF_VARIANT;
+compile_const bool c_input_is_premult = DEF_INPUT_IS_PREMULT;
compile_const bool c_green_tint = DEF_GREEN_TINT;
vec4
@@ -79,7 +80,6 @@ yuva2rgba(vec4 yuva)
color_out.g = Y - 0.39176229 * su - 0.81296764 * sv;
color_out.b = Y + 2.01723214 * su;
- color_out.rgb *= yuva.w;
color_out.a = yuva.w;
return color_out;
@@ -141,16 +141,31 @@ sample_input_texture()
return yuva2rgba(yuva);
}
+vec4
+pipeline_premult(vec4 color, compile_const bool input_is_premult)
+{
+ /* Ensure premultiplied alpha, apply view alpha (opacity) */
+ if (input_is_premult) {
+ color *= alpha;
+ } else {
+ color.a *= alpha;
+ color.rgb *= color.a;
+ }
+
+ return color;
+}
+
void
main()
{
vec4 color;
- /* Electrical (non-linear) RGBA values, pre-multiplied */
+ /* Electrical (non-linear) RGBA values, may be premult or not */
color = sample_input_texture();
- /* View alpha (opacity) */
- color *= alpha;
+ color = pipeline_premult(color, c_input_is_premult);
+
+ /* color is guaranteed premult here */
if (c_green_tint)
color = vec4(0.0, 0.3, 0.0, 0.2) + color * 0.8;
diff --git a/libweston/renderer-gl/gl-renderer-internal.h b/libweston/renderer-gl/gl-renderer-internal.h
index cf2476dba6..0beb1dc64c 100644
--- a/libweston/renderer-gl/gl-renderer-internal.h
+++ b/libweston/renderer-gl/gl-renderer-internal.h
@@ -62,13 +62,14 @@ enum gl_shader_texture_variant {
struct gl_shader_requirements
{
unsigned variant:4; /* enum gl_shader_texture_variant */
+ bool input_is_premult:1;
bool green_tint:1;
/*
* The total size of all bitfields plus pad_bits_ must fill up exactly
* how many bytes the compiler allocates for them together.
*/
- unsigned pad_bits_:27;
+ unsigned pad_bits_:26;
};
static_assert(sizeof(struct gl_shader_requirements) ==
4 /* total bitfield size in bytes */,
@@ -202,6 +203,9 @@ gl_renderer_setup_egl_extensions(struct weston_compositor *ec);
GLenum
gl_shader_texture_variant_get_target(enum gl_shader_texture_variant v);
+bool
+gl_shader_texture_variant_can_be_premult(enum gl_shader_texture_variant v);
+
void
gl_shader_destroy(struct gl_renderer *gr, struct gl_shader *shader);
diff --git a/libweston/renderer-gl/gl-renderer.c b/libweston/renderer-gl/gl-renderer.c
index f4ee68916d..5f9b8c2d28 100644
--- a/libweston/renderer-gl/gl-renderer.c
+++ b/libweston/renderer-gl/gl-renderer.c
@@ -738,6 +738,7 @@ triangle_fan_debug(struct gl_renderer *gr,
alt = (struct gl_shader_config) {
.req = {
.variant = SHADER_VARIANT_SOLID,
+ .input_is_premult = true,
},
.projection = sconf->projection,
.view_alpha = 1.0f,
@@ -925,6 +926,7 @@ maybe_censor_override(struct gl_shader_config *sconf,
const struct gl_shader_config alt = {
.req = {
.variant = SHADER_VARIANT_SOLID,
+ .input_is_premult = true,
},
.projection = sconf->projection,
.view_alpha = sconf->view_alpha,
@@ -960,6 +962,8 @@ gl_shader_config_set_input_textures(struct gl_shader_config *sconf,
int i;
sconf->req.variant = gs->shader_variant;
+ sconf->req.input_is_premult =
+ gl_shader_texture_variant_can_be_premult(gs->shader_variant);
for (i = 0; i < 4; i++)
sconf->unicolor[i] = gs->color[i];
@@ -1264,6 +1268,7 @@ draw_output_borders(struct weston_output *output,
struct gl_shader_config sconf = {
.req = {
.variant = SHADER_VARIANT_RGBA,
+ .input_is_premult = true,
},
.view_alpha = 1.0f,
};
@@ -1488,6 +1493,7 @@ blit_shadow_to_output(struct weston_output *output,
const struct gl_shader_config sconf = {
.req = {
.variant = SHADER_VARIANT_RGBA,
+ .input_is_premult = true,
},
.projection = {
.d = { /* transpose */
diff --git a/libweston/renderer-gl/gl-shaders.c b/libweston/renderer-gl/gl-shaders.c
index 4a47ca986c..0b1c8cfb1f 100644
--- a/libweston/renderer-gl/gl-shaders.c
+++ b/libweston/renderer-gl/gl-shaders.c
@@ -147,8 +147,9 @@ create_shader_description_string(const struct gl_shader_requirements *req)
int size;
char *str;
- size = asprintf(&str, "%s %cgreen",
+ size = asprintf(&str, "%s %cinput_is_premult %cgreen",
gl_shader_texture_variant_to_string(req->variant),
+ req->input_is_premult ? '+' : '-',
req->green_tint ? '+' : '-');
if (size < 0)
return NULL;
@@ -163,8 +164,10 @@ create_shader_config_string(const struct gl_shader_requirements *req)
size = asprintf(&str,
"#define DEF_GREEN_TINT %s\n"
+ "#define DEF_INPUT_IS_PREMULT %s\n"
"#define DEF_VARIANT %s\n",
req->green_tint ? "true" : "false",
+ req->input_is_premult ? "true" : "false",
gl_shader_texture_variant_to_string(req->variant));
if (size < 0)
return NULL;
@@ -349,6 +352,7 @@ gl_renderer_create_fallback_shader(struct gl_renderer *gr)
{
static const struct gl_shader_requirements fallback_requirements = {
.variant = SHADER_VARIANT_SOLID,
+ .input_is_premult = true,
};
struct gl_shader *shader;
@@ -415,6 +419,25 @@ gl_renderer_garbage_collect_programs(struct gl_renderer *gr)
}
}
+bool
+gl_shader_texture_variant_can_be_premult(enum gl_shader_texture_variant v)
+{
+ switch (v) {
+ case SHADER_VARIANT_SOLID:
+ case SHADER_VARIANT_RGBA:
+ case SHADER_VARIANT_EXTERNAL:
+ return true;
+ case SHADER_VARIANT_NONE:
+ case SHADER_VARIANT_RGBX:
+ case SHADER_VARIANT_Y_U_V:
+ case SHADER_VARIANT_Y_UV:
+ case SHADER_VARIANT_Y_XUXV:
+ case SHADER_VARIANT_XYUV:
+ return false;
+ }
+ return true;
+}
+
GLenum
gl_shader_texture_variant_get_target(enum gl_shader_texture_variant v)
{
--
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