video/screen: Make RGB frames without alpha

video/software/src/decoder/screen.rs

@@ -190,28 +190,25 @@ impl VideoDecoder for ScreenVideoDecoder {
             return Err(ScreenError::KeyframeInvalid.into());
         }
 
-        let mut rgba = vec![0u8; w * h * 4];
+        let mut rgb = vec![0u8; w * h * 3];
 
-        // convert from BGR to RGBA and flip Y
+        // convert from BGR to RGB and flip Y
         for y in 0..h {
             let data_row = &data[y * w * 3..(y + 1) * w * 3];
-            let rgba_row = &mut rgba[(h - y - 1) * w * 4..(h - y) * w * 4];
+            let rgb_row = &mut rgb[(h - y - 1) * w * 3..(h - y) * w * 3];
 
-            for (bgr, rgba) in data_row.chunks(3).zip(rgba_row.chunks_mut(4)) {
-                rgba.copy_from_slice(&[bgr[2], bgr[1], bgr[0], 255]);
+            for (bgr, rgb) in data_row.chunks(3).zip(rgb_row.chunks_mut(3)) {
+                rgb.copy_from_slice(&[bgr[2], bgr[1], bgr[0]]);
             }
         }
 
         self.last_frame = Some(data);
 
-        // NOTE: We could get away with only storing RGB data (saving some memory), as there is no
-        // alpha support in Screen V1, but since the render backends always want RGBA right now,
-        // it's better to do the pixel format conversion here, all at once.
         Ok(DecodedFrame::new(
             w as u32,
             h as u32,
-            BitmapFormat::Rgba,
-            rgba,
+            BitmapFormat::Rgb,
+            rgb,
         ))
     }
 }