[libcamera-devel] [PATCH 3/3] qcam: viewfinder_gl: Take color space into account for YUV rendering
Laurent Pinchart
laurent.pinchart at ideasonboard.com
Mon Aug 29 12:04:14 CEST 2022
Update the YUV shaders and the viewfinder_gl to correctly take the
Y'CbCr encoding and the quantization range into account when rendering
YUV formats to RGB. Support for the primaries and transfer function will
be added in a subsequent step.
Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
---
src/qcam/assets/shader/YUV_2_planes.frag | 27 ++++----
src/qcam/assets/shader/YUV_3_planes.frag | 23 ++++---
src/qcam/assets/shader/YUV_packed.frag | 17 ++---
src/qcam/viewfinder_gl.cpp | 79 +++++++++++++++++++++++-
src/qcam/viewfinder_gl.h | 2 +
5 files changed, 115 insertions(+), 33 deletions(-)
diff --git a/src/qcam/assets/shader/YUV_2_planes.frag b/src/qcam/assets/shader/YUV_2_planes.frag
index 254463c05cac..da8dbcc5f801 100644
--- a/src/qcam/assets/shader/YUV_2_planes.frag
+++ b/src/qcam/assets/shader/YUV_2_planes.frag
@@ -13,27 +13,30 @@ varying vec2 textureOut;
uniform sampler2D tex_y;
uniform sampler2D tex_u;
+const mat3 yuv2rgb_matrix = mat3(
+ YUV2RGB_MATRIX
+);
+
+const vec3 yuv2rgb_offset = vec3(
+ YUV2RGB_Y_OFFSET / 255.0, 128.0 / 255.0, 128.0 / 255.0
+);
+
void main(void)
{
vec3 yuv;
- vec3 rgb;
- 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)
- );
- yuv.x = texture2D(tex_y, textureOut).r - 0.063;
+ yuv.x = texture2D(tex_y, textureOut).r;
#if defined(YUV_PATTERN_UV)
- yuv.y = texture2D(tex_u, textureOut).r - 0.500;
- yuv.z = texture2D(tex_u, textureOut).a - 0.500;
+ yuv.y = texture2D(tex_u, textureOut).r;
+ yuv.z = texture2D(tex_u, textureOut).a;
#elif defined(YUV_PATTERN_VU)
- yuv.y = texture2D(tex_u, textureOut).a - 0.500;
- yuv.z = texture2D(tex_u, textureOut).r - 0.500;
+ yuv.y = texture2D(tex_u, textureOut).a;
+ yuv.z = texture2D(tex_u, textureOut).r;
#else
#error Invalid pattern
#endif
- rgb = yuv2rgb_bt601_mat * yuv;
+ vec3 rgb = yuv2rgb_matrix * (vec3(y, uv) - yuv2rgb_offset);
+
gl_FragColor = vec4(rgb, 1.0);
}
diff --git a/src/qcam/assets/shader/YUV_3_planes.frag b/src/qcam/assets/shader/YUV_3_planes.frag
index 2be74b5d2a9d..e754129d74d1 100644
--- a/src/qcam/assets/shader/YUV_3_planes.frag
+++ b/src/qcam/assets/shader/YUV_3_planes.frag
@@ -14,20 +14,23 @@ uniform sampler2D tex_y;
uniform sampler2D tex_u;
uniform sampler2D tex_v;
+const mat3 yuv2rgb_matrix = mat3(
+ YUV2RGB_MATRIX
+);
+
+const vec3 yuv2rgb_offset = vec3(
+ YUV2RGB_Y_OFFSET / 255.0, 128.0 / 255.0, 128.0 / 255.0
+);
+
void main(void)
{
vec3 yuv;
- vec3 rgb;
- 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)
- );
- yuv.x = texture2D(tex_y, textureOut).r - 0.063;
- yuv.y = texture2D(tex_u, textureOut).r - 0.500;
- yuv.z = texture2D(tex_v, textureOut).r - 0.500;
+ yuv.x = texture2D(tex_y, textureOut).r;
+ yuv.y = texture2D(tex_u, textureOut).r;
+ yuv.z = texture2D(tex_v, textureOut).r;
+
+ vec3 rgb = yuv2rgb_matrix * (vec3(y, uv) - yuv2rgb_offset);
- rgb = yuv2rgb_bt601_mat * yuv;
gl_FragColor = vec4(rgb, 1.0);
}
diff --git a/src/qcam/assets/shader/YUV_packed.frag b/src/qcam/assets/shader/YUV_packed.frag
index d6efd4ce92a9..b9ef9d41beae 100644
--- a/src/qcam/assets/shader/YUV_packed.frag
+++ b/src/qcam/assets/shader/YUV_packed.frag
@@ -14,15 +14,16 @@ varying vec2 textureOut;
uniform sampler2D tex_y;
uniform vec2 tex_step;
+const mat3 yuv2rgb_matrix = mat3(
+ YUV2RGB_MATRIX
+);
+
+const vec3 yuv2rgb_offset = vec3(
+ YUV2RGB_Y_OFFSET / 255.0, 128.0 / 255.0, 128.0 / 255.0
+);
+
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
@@ -76,7 +77,7 @@ void main(void)
float y = mix(y_left, y_right, step(0.5, f_x));
- vec3 rgb = yuv2rgb_bt601_mat * (vec3(y, uv) - yuv2rgb_bt601_offset);
+ vec3 rgb = yuv2rgb_matrix * (vec3(y, uv) - yuv2rgb_offset);
gl_FragColor = vec4(rgb, 1.0);
}
diff --git a/src/qcam/viewfinder_gl.cpp b/src/qcam/viewfinder_gl.cpp
index ec295b6de0dd..e2aa24703ff0 100644
--- a/src/qcam/viewfinder_gl.cpp
+++ b/src/qcam/viewfinder_gl.cpp
@@ -7,9 +7,12 @@
#include "viewfinder_gl.h"
+#include <array>
+
#include <QByteArray>
#include <QFile>
#include <QImage>
+#include <QStringList>
#include <libcamera/formats.h>
@@ -56,7 +59,8 @@ static const QList<libcamera::PixelFormat> supportedFormats{
};
ViewFinderGL::ViewFinderGL(QWidget *parent)
- : QOpenGLWidget(parent), buffer_(nullptr), image_(nullptr),
+ : QOpenGLWidget(parent), buffer_(nullptr),
+ colorSpace_(libcamera::ColorSpace::Raw), image_(nullptr),
vertexBuffer_(QOpenGLBuffer::VertexBuffer)
{
}
@@ -72,10 +76,10 @@ const QList<libcamera::PixelFormat> &ViewFinderGL::nativeFormats() const
}
int ViewFinderGL::setFormat(const libcamera::PixelFormat &format, const QSize &size,
- [[maybe_unused]] const libcamera::ColorSpace &colorSpace,
+ const libcamera::ColorSpace &colorSpace,
unsigned int stride)
{
- if (format != format_) {
+ if (format != format_ || colorSpace != colorSpace_) {
/*
* If the fragment already exists, remove it and create a new
* one for the new format.
@@ -89,7 +93,10 @@ int ViewFinderGL::setFormat(const libcamera::PixelFormat &format, const QSize &s
if (!selectFormat(format))
return -1;
+ selectColorSpace(colorSpace);
+
format_ = format;
+ colorSpace_ = colorSpace;
}
size_ = size;
@@ -318,6 +325,72 @@ bool ViewFinderGL::selectFormat(const libcamera::PixelFormat &format)
return ret;
}
+void ViewFinderGL::selectColorSpace(const libcamera::ColorSpace &colorSpace)
+{
+ std::array<double, 9> yuv2rgb;
+
+ /* OpenGL stores arrays in column-major order. */
+ switch (colorSpace.ycbcrEncoding) {
+ case libcamera::ColorSpace::YcbcrEncoding::None:
+ yuv2rgb = {
+ 1.0000, 0.0000, 0.0000,
+ 0.0000, 1.0000, 0.0000,
+ 0.0000, 0.0000, 1.0000,
+ };
+ break;
+
+ case libcamera::ColorSpace::YcbcrEncoding::Rec601:
+ yuv2rgb = {
+ 1.0000, 1.0000, 1.0000,
+ 0.0000, -0.3441, 1.7720,
+ 1.4020, -0.7141, 0.0000,
+ };
+ break;
+
+ case libcamera::ColorSpace::YcbcrEncoding::Rec709:
+ yuv2rgb = {
+ 1.0000, 1.0000, 1.0000,
+ 0.0000, -0.1873, 1.8856,
+ 1.5748, -0.4681, 0.0000,
+ };
+ break;
+
+ case libcamera::ColorSpace::YcbcrEncoding::Rec2020:
+ yuv2rgb = {
+ 1.0000, 1.0000, 1.0000,
+ 0.0000, -0.1646, 1.8814,
+ 1.4746, -0.5714, 0.0000,
+ };
+ break;
+ }
+
+ double offset;
+
+ switch (colorSpace.range) {
+ case libcamera::ColorSpace::Range::Full:
+ offset = 0.0;
+ break;
+
+ case libcamera::ColorSpace::Range::Limited:
+ offset = 16.0;
+
+ for (unsigned int i = 0; i < 3; ++i)
+ yuv2rgb[i] *= 255.0 / 219.0;
+ for (unsigned int i = 4; i < 9; ++i)
+ yuv2rgb[i] *= 255.0 / 224.0;
+ break;
+ }
+
+ QStringList matrix;
+
+ for (double coeff : yuv2rgb)
+ matrix.append(QString::number(coeff, 'f'));
+
+ fragmentShaderDefines_.append("#define YUV2RGB_MATRIX " + matrix.join(", "));
+ fragmentShaderDefines_.append(QString("#define YUV2RGB_Y_OFFSET %1")
+ .arg(offset, 0, 'f', 1));
+}
+
bool ViewFinderGL::createVertexShader()
{
/* Create Vertex Shader */
diff --git a/src/qcam/viewfinder_gl.h b/src/qcam/viewfinder_gl.h
index 798830a31cd2..68c2912df12f 100644
--- a/src/qcam/viewfinder_gl.h
+++ b/src/qcam/viewfinder_gl.h
@@ -57,6 +57,7 @@ protected:
private:
bool selectFormat(const libcamera::PixelFormat &format);
+ void selectColorSpace(const libcamera::ColorSpace &colorSpace);
void configureTexture(QOpenGLTexture &texture);
bool createFragmentShader();
@@ -67,6 +68,7 @@ private:
/* Captured image size, format and buffer */
libcamera::FrameBuffer *buffer_;
libcamera::PixelFormat format_;
+ libcamera::ColorSpace colorSpace_;
QSize size_;
unsigned int stride_;
Image *image_;
--
Regards,
Laurent Pinchart
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