From 93feffad15fe68dc97278df9e6726135e31b6474 Mon Sep 17 00:00:00 2001
From: wm4 <wm4@nowhere>
Date: Thu, 19 Sep 2013 16:55:56 +0200
Subject: vo_opengl: blend alpha components by default

Improves display of images and video with alpha channel, especially if
the transparent regions contain (supposed to be invisible) garbage
color values.
---
 video/out/gl_video.c            | 14 ++++++++++----
 video/out/gl_video.h            |  2 +-
 video/out/gl_video_shaders.glsl |  3 +++
 video/out/vo_opengl.c           |  2 +-
 4 files changed, 15 insertions(+), 6 deletions(-)

(limited to 'video')

diff --git a/video/out/gl_video.c b/video/out/gl_video.c
index ff5bbc7d47..21efc6dd56 100644
--- a/video/out/gl_video.c
+++ b/video/out/gl_video.c
@@ -271,6 +271,7 @@ static const struct gl_video_opts gl_video_opts_def = {
     .scale_sep = 1,
     .scalers = { "bilinear", "bilinear" },
     .scaler_params = {NAN, NAN},
+    .alpha_mode = 2,
 };
 
 
@@ -319,7 +320,10 @@ const struct m_sub_options gl_video_conf = {
                    ({"auto",   MP_CHROMA_AUTO},
                     {"center", MP_CHROMA_CENTER},
                     {"left",   MP_CHROMA_LEFT})),
-        OPT_FLAG("alpha", enable_alpha, 0),
+        OPT_CHOICE("alpha", alpha_mode, M_OPT_OPTIONAL_PARAM,
+                   ({"no", 0},
+                    {"yes", 1}, {"", 1},
+                    {"blend", 2})),
         {0}
     },
     .size = sizeof(struct gl_video_opts),
@@ -779,8 +783,8 @@ static void compile_shaders(struct gl_video *p)
                                    shader_prelude, PRELUDE_END);
 
     // Need to pass alpha through the whole chain. (Not needed for OSD shaders.)
-    bool use_alpha = p->opts.enable_alpha && p->has_alpha;
-    shader_def_opt(&header, "USE_ALPHA", use_alpha);
+    if (p->opts.alpha_mode == 1)
+        shader_def_opt(&header, "USE_ALPHA", p->has_alpha);
 
     char *header_osd = talloc_strdup(tmp, header);
     shader_def_opt(&header_osd, "USE_OSD_LINEAR_CONV", p->opts.srgb &&
@@ -831,8 +835,10 @@ static void compile_shaders(struct gl_video *p)
     shader_def_opt(&header_conv, "USE_INPUT_GAMMA", convert_input_gamma);
     shader_def_opt(&header_conv, "USE_COLORMATRIX", !p->is_rgb);
     shader_def_opt(&header_conv, "USE_CONV_GAMMA", convert_input_to_linear);
-    if (use_alpha && p->plane_count > 3)
+    if (p->opts.alpha_mode > 0 && p->has_alpha && p->plane_count > 3)
         shader_def(&header_conv, "USE_ALPHA_PLANE", "3");
+    if (p->opts.alpha_mode == 2 && p->has_alpha)
+        shader_def(&header_conv, "USE_ALPHA_BLEND", "1");
 
     shader_def_opt(&header_final, "USE_LINEAR_CONV_INV", p->use_lut_3d);
     shader_def_opt(&header_final, "USE_GAMMA_POW", p->opts.gamma);
diff --git a/video/out/gl_video.h b/video/out/gl_video.h
index bc21310498..3b21edc223 100644
--- a/video/out/gl_video.h
+++ b/video/out/gl_video.h
@@ -44,7 +44,7 @@ struct gl_video_opts {
     int temporal_dither;
     int fbo_format;
     int stereo_mode;
-    int enable_alpha;
+    int alpha_mode;
     int chroma_location;
 };
 
diff --git a/video/out/gl_video_shaders.glsl b/video/out/gl_video_shaders.glsl
index 8ca6739bf4..b0df20b544 100644
--- a/video/out/gl_video_shaders.glsl
+++ b/video/out/gl_video_shaders.glsl
@@ -387,6 +387,9 @@ void main() {
     color = floor(color * dither_quantization + dither_value + dither_center) /
                 dither_quantization;
 #endif
+#ifdef USE_ALPHA_BLEND
+    color = color * alpha;
+#endif
 #ifdef USE_ALPHA
     out_color = vec4(color, alpha);
 #else
diff --git a/video/out/vo_opengl.c b/video/out/vo_opengl.c
index 7f4c05ac58..03d1689667 100644
--- a/video/out/vo_opengl.c
+++ b/video/out/vo_opengl.c
@@ -144,7 +144,7 @@ static bool config_window(struct gl_priv *p, uint32_t d_width,
     if (p->renderer_opts->stereo_mode == GL_3D_QUADBUFFER)
         flags |= VOFLAG_STEREO;
 
-    if (p->renderer_opts->enable_alpha)
+    if (p->renderer_opts->alpha_mode == 1)
         flags |= VOFLAG_ALPHA;
 
     if (p->use_gl_debug)
-- 
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