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authorLaurent Pinchart <laurent.pinchart@ideasonboard.com>2020-09-13 01:04:20 +0300
committerLaurent Pinchart <laurent.pinchart@ideasonboard.com>2020-10-04 22:51:45 +0300
commitdcc47ff715ef1a8b97df53c810ec0c4b069b06e5 (patch)
treedcfb3fc39fa69ec4c04bfa68550834dee075770f /src/qcam/assets/shader
parentae9e7fbf3a8bf45b08951b650aec3f91997fafc3 (diff)
qcam: viewfinder_gl: Add shader to render packed YUV formats
The shader supports all 4 packed 8-bit YUV variants. Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Acked-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Diffstat (limited to 'src/qcam/assets/shader')
-rw-r--r--src/qcam/assets/shader/YUV_packed.frag82
-rw-r--r--src/qcam/assets/shader/shaders.qrc1
2 files changed, 83 insertions, 0 deletions
diff --git a/src/qcam/assets/shader/YUV_packed.frag b/src/qcam/assets/shader/YUV_packed.frag
new file mode 100644
index 00000000..224dfafe
--- /dev/null
+++ b/src/qcam/assets/shader/YUV_packed.frag
@@ -0,0 +1,82 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2020, Laurent Pinchart <laurent.pinchart@ideasonboard.com>
+ *
+ * YUV_packed.frag - Fragment shader code for YUYV packed formats
+ */
+
+#ifdef GL_ES
+precision mediump float;
+#endif
+
+varying vec2 textureOut;
+
+uniform sampler2D tex_y;
+uniform float tex_stepx;
+
+void main(void)
+{
+ mat3 yuv2rgb_bt601_mat = mat3(
+ vec3(1.164, 1.164, 1.164),
+ vec3(0.000, -0.392, 2.017),
+ vec3(1.596, -0.813, 0.000)
+ );
+ vec3 yuv2rgb_bt601_offset = vec3(0.063, 0.500, 0.500);
+
+ /*
+ * The sampler won't interpolate the texture correctly along the X axis,
+ * as each RGBA pixel effectively stores two pixels. We thus need to
+ * interpolate manually.
+ *
+ * In integer texture coordinates, the Y values are layed out in the
+ * texture memory as follows:
+ *
+ * ...| Y U Y V | Y U Y V | Y U Y V |...
+ * ...| R G B A | R G B A | R G B A |...
+ * ^ ^ ^ ^ ^ ^
+ * | | | | | |
+ * n-1 n-0.5 n n+0.5 n+1 n+1.5
+ *
+ * For a texture location x in the interval [n, n+1[, sample the left
+ * and right pixels at n and n+1, and interpolate them with
+ *
+ * left.r * (1 - a) + left.b * a if fract(x) < 0.5
+ * left.b * (1 - a) + right.r * a if fract(x) >= 0.5
+ *
+ * with a = fract(x * 2) which can also be written
+ *
+ * a = fract(x) * 2 if fract(x) < 0.5
+ * a = fract(x) * 2 - 1 if fract(x) >= 0.5
+ */
+ vec2 pos = textureOut;
+ float f_x = fract(pos.x / tex_stepx);
+
+ vec4 left = texture2D(tex_y, vec2(pos.x - f_x * tex_stepx, pos.y));
+ vec4 right = texture2D(tex_y, vec2(pos.x + (1.0 - f_x) * tex_stepx , pos.y));
+
+#if defined(YUV_PATTERN_UYVY)
+ float y_left = mix(left.g, left.a, f_x * 2.0);
+ float y_right = mix(left.a, right.g, f_x * 2.0 - 1.0);
+ vec2 uv = mix(left.rb, right.rb, f_x);
+#elif defined(YUV_PATTERN_VYUY)
+ float y_left = mix(left.g, left.a, f_x * 2.0);
+ float y_right = mix(left.a, right.g, f_x * 2.0 - 1.0);
+ vec2 uv = mix(left.br, right.br, f_x);
+#elif defined(YUV_PATTERN_YUYV)
+ float y_left = mix(left.r, left.b, f_x * 2.0);
+ float y_right = mix(left.b, right.r, f_x * 2.0 - 1.0);
+ vec2 uv = mix(left.ga, right.ga, f_x);
+#elif defined(YUV_PATTERN_YVYU)
+ float y_left = mix(left.r, left.b, f_x * 2.0);
+ float y_right = mix(left.b, right.r, f_x * 2.0 - 1.0);
+ vec2 uv = mix(left.ag, right.ag, f_x);
+#else
+#error Invalid pattern
+#endif
+
+ float y = mix(y_left, y_right, step(0.5, f_x));
+
+ vec3 rgb = yuv2rgb_bt601_mat * (vec3(y, uv) - yuv2rgb_bt601_offset);
+
+ gl_FragColor = vec4(rgb, 1.0);
+}
diff --git a/src/qcam/assets/shader/shaders.qrc b/src/qcam/assets/shader/shaders.qrc
index 7010d843..857ed9fd 100644
--- a/src/qcam/assets/shader/shaders.qrc
+++ b/src/qcam/assets/shader/shaders.qrc
@@ -4,5 +4,6 @@
<file>YUV.vert</file>
<file>YUV_2_planes.frag</file>
<file>YUV_3_planes.frag</file>
+ <file>YUV_packed.frag</file>
</qresource>
</RCC>