[vlc-devel] [PATCH v2 16/29] opengl: apply subpictures alpha

[Alexandre Janniaux]

Hi,

Comments inline,

On Thu, Feb 06, 2020 at 02:17:45PM +0100, Romain Vimont wrote:
> The new subpictures renderer did not apply the alpha value.
> ---
>  modules/video_output/opengl/sub_renderer.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/modules/video_output/opengl/sub_renderer.c b/modules/video_output/opengl/sub_renderer.c
> index 2bea0b149c..ec9afe3d60 100644
> --- a/modules/video_output/opengl/sub_renderer.c
> +++ b/modules/video_output/opengl/sub_renderer.c
> @@ -75,6 +75,7 @@ struct vlc_gl_sub_renderer
>      } aloc;
>      struct {
>          GLint sampler;
> +        GLint alpha;
>      } uloc;
>
>      GLuint *buffer_objects;
> @@ -159,9 +160,11 @@ CreateProgram(vlc_object_t *obj, const opengl_vtable_t *vt)
>          "#version 100\n"
>          "precision mediump float;\n"
>          "uniform sampler2D sampler;\n"
> +        "uniform float alpha;\n"
>          "varying vec2 tex_coords;\n"
>          "void main() {\n"
> -        "  gl_FragColor = texture2D(sampler, tex_coords);\n"
> +        "  vec4 color = texture2D(sampler, tex_coords);\n"
> +        "  gl_FragColor = vec4(1.0, 1.0, 1.0, alpha) * color;\n"

It might be cleaner with:

gl_FragColor = vec4(color.rgb, color.a * alpha);

or

color.a *= alpha;
gl_FragColor = color;

>          "}\n";
>
>      GLuint program = 0;
> @@ -222,6 +225,7 @@ FetchLocations(struct vlc_gl_sub_renderer *sr)
>  #define GET_ULOC(x, str) GET_LOC(Uniform, x, str)
>  #define GET_ALOC(x, str) GET_LOC(Attrib, x, str)
>      GET_ULOC(sr->uloc.sampler, "sampler");
> +    GET_ULOC(sr->uloc.alpha, "alpha");
>      GET_ALOC(sr->aloc.vertex_pos, "vertex_pos");
>      GET_ALOC(sr->aloc.tex_coords_in, "tex_coords_in");
>
> @@ -448,6 +452,8 @@ vlc_gl_sub_renderer_Draw(struct vlc_gl_sub_renderer *sr)
>          assert(glr->texture != 0);
>          vt->BindTexture(interop->tex_target, glr->texture);
>
> +        vt->Uniform1f(sr->uloc.alpha, glr->alpha);
> +
>          vt->BindBuffer(GL_ARRAY_BUFFER, sr->buffer_objects[2 * i]);
>          vt->BufferData(GL_ARRAY_BUFFER, sizeof(textureCoord), textureCoord, GL_STATIC_DRAW);
>          vt->EnableVertexAttribArray(sr->aloc.tex_coords_in);
> --
> 2.25.0
>
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