qcam: viewfinder_gl: Support configurable stride in shaders

The RGB and YUV conversion doesn't take the stride into account, neither
when creating the textures, nor when sampling them. Fix it by using the
stride as the texture width, and multiplying the x coordinate in the
vertex shaders by a factor to only sample the active portion of the
image.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>

3 files changed, 47 insertions, 12 deletions

diff --git a/src/qcam/assets/shader/identity.vert b/src/qcam/assets/shader/identity.vert
index 6d6f7551..12c41377 100644
--- a/src/qcam/assets/shader/identity.vert
+++ b/src/qcam/assets/shader/identity.vert
@@ -9,8 +9,10 @@ attribute vec4 vertexIn;
 attribute vec2 textureIn;
 varying vec2 textureOut;
 
+uniform float stride_factor;
+
 void main(void)
 {
 	gl_Position = vertexIn;
-	textureOut = textureIn;
+	textureOut = vec2(textureIn.x * stride_factor, textureIn.y);
 }
diff --git a/src/qcam/viewfinder_gl.cpp b/src/qcam/viewfinder_gl.cpp
index aeb1ea02..3ae8b03a 100644
--- a/src/qcam/viewfinder_gl.cpp
+++ b/src/qcam/viewfinder_gl.cpp
@@ -395,6 +395,7 @@ bool ViewFinderGL::createFragmentShader()
 	textureUniformV_ = shaderProgram_.uniformLocation("tex_v");
 	textureUniformStep_ = shaderProgram_.uniformLocation("tex_step");
 	textureUniformSize_ = shaderProgram_.uniformLocation("tex_size");
+	textureUniformStrideFactor_ = shaderProgram_.uniformLocation("stride_factor");
 	textureUniformBayerFirstRed_ = shaderProgram_.uniformLocation("tex_bayer_first_red");
 
 	/* Create the textures. */
@@ -464,6 +465,9 @@ void ViewFinderGL::initializeGL()
 
 void ViewFinderGL::doRender()
 {
+	/* Stride of the first plane, in pixels. */
+	unsigned int stridePixels;
+
 	switch (format_) {
 	case libcamera::formats::NV12:
 	case libcamera::formats::NV21:
@@ -477,7 +481,7 @@ void ViewFinderGL::doRender()
 		glTexImage2D(GL_TEXTURE_2D,
 			     0,
 			     GL_LUMINANCE,
-			     size_.width(),
+			     stride_,
 			     size_.height(),
 			     0,
 			     GL_LUMINANCE,
@@ -491,13 +495,15 @@ void ViewFinderGL::doRender()
 		glTexImage2D(GL_TEXTURE_2D,
 			     0,
 			     GL_LUMINANCE_ALPHA,
-			     size_.width() / horzSubSample_,
+			     stride_ / horzSubSample_,
 			     size_.height() / vertSubSample_,
 			     0,
 			     GL_LUMINANCE_ALPHA,
 			     GL_UNSIGNED_BYTE,
 			     image_->data(1).data());
 		shaderProgram_.setUniformValue(textureUniformU_, 1);
+
+		stridePixels = stride_;
 		break;
 
 	case libcamera::formats::YUV420:
@@ -507,7 +513,7 @@ void ViewFinderGL::doRender()
 		glTexImage2D(GL_TEXTURE_2D,
 			     0,
 			     GL_LUMINANCE,
-			     size_.width(),
+			     stride_,
 			     size_.height(),
 			     0,
 			     GL_LUMINANCE,
@@ -521,7 +527,7 @@ void ViewFinderGL::doRender()
 		glTexImage2D(GL_TEXTURE_2D,
 			     0,
 			     GL_LUMINANCE,
-			     size_.width() / horzSubSample_,
+			     stride_ / horzSubSample_,
 			     size_.height() / vertSubSample_,
 			     0,
 			     GL_LUMINANCE,
@@ -535,13 +541,15 @@ void ViewFinderGL::doRender()
 		glTexImage2D(GL_TEXTURE_2D,
 			     0,
 			     GL_LUMINANCE,
-			     size_.width() / horzSubSample_,
+			     stride_ / horzSubSample_,
 			     size_.height() / vertSubSample_,
 			     0,
 			     GL_LUMINANCE,
 			     GL_UNSIGNED_BYTE,
 			     image_->data(2).data());
 		shaderProgram_.setUniformValue(textureUniformV_, 2);
+
+		stridePixels = stride_;
 		break;
 
 	case libcamera::formats::YVU420:
@@ -551,7 +559,7 @@ void ViewFinderGL::doRender()
 		glTexImage2D(GL_TEXTURE_2D,
 			     0,
 			     GL_LUMINANCE,
-			     size_.width(),
+			     stride_,
 			     size_.height(),
 			     0,
 			     GL_LUMINANCE,
@@ -565,7 +573,7 @@ void ViewFinderGL::doRender()
 		glTexImage2D(GL_TEXTURE_2D,
 			     0,
 			     GL_LUMINANCE,
-			     size_.width() / horzSubSample_,
+			     stride_ / horzSubSample_,
 			     size_.height() / vertSubSample_,
 			     0,
 			     GL_LUMINANCE,
@@ -579,13 +587,15 @@ void ViewFinderGL::doRender()
 		glTexImage2D(GL_TEXTURE_2D,
 			     0,
 			     GL_LUMINANCE,
-			     size_.width() / horzSubSample_,
+			     stride_ / horzSubSample_,
 			     size_.height() / vertSubSample_,
 			     0,
 			     GL_LUMINANCE,
 			     GL_UNSIGNED_BYTE,
 			     image_->data(2).data());
 		shaderProgram_.setUniformValue(textureUniformU_, 1);
+
+		stridePixels = stride_;
 		break;
 
 	case libcamera::formats::UYVY:
@@ -602,7 +612,7 @@ void ViewFinderGL::doRender()
 		glTexImage2D(GL_TEXTURE_2D,
 			     0,
 			     GL_RGBA,
-			     size_.width() / 2,
+			     stride_ / 4,
 			     size_.height(),
 			     0,
 			     GL_RGBA,
@@ -619,6 +629,8 @@ void ViewFinderGL::doRender()
 		shaderProgram_.setUniformValue(textureUniformStep_,
 					       1.0f / (size_.width() / 2 - 1),
 					       1.0f /* not used */);
+
+		stridePixels = stride_ / 2;
 		break;
 
 	case libcamera::formats::ABGR8888:
@@ -630,13 +642,15 @@ void ViewFinderGL::doRender()
 		glTexImage2D(GL_TEXTURE_2D,
 			     0,
 			     GL_RGBA,
-			     size_.width(),
+			     stride_ / 4,
 			     size_.height(),
 			     0,
 			     GL_RGBA,
 			     GL_UNSIGNED_BYTE,
 			     image_->data(0).data());
 		shaderProgram_.setUniformValue(textureUniformY_, 0);
+
+		stridePixels = stride_ / 4;
 		break;
 
 	case libcamera::formats::BGR888:
@@ -646,13 +660,15 @@ void ViewFinderGL::doRender()
 		glTexImage2D(GL_TEXTURE_2D,
 			     0,
 			     GL_RGB,
-			     size_.width(),
+			     stride_ / 3,
 			     size_.height(),
 			     0,
 			     GL_RGB,
 			     GL_UNSIGNED_BYTE,
 			     image_->data(0).data());
 		shaderProgram_.setUniformValue(textureUniformY_, 0);
+
+		stridePixels = stride_ / 3;
 		break;
 
 	case libcamera::formats::SBGGR8:
@@ -692,11 +708,27 @@ void ViewFinderGL::doRender()
 		shaderProgram_.setUniformValue(textureUniformStep_,
 					       1.0f / (stride_ - 1),
 					       1.0f / (size_.height() - 1));
+
+		/*
+		 * The stride is already taken into account in the shaders, set
+		 * the generic stride factor to 1.0.
+		 */
+		stridePixels = size_.width();
 		break;
 
 	default:
+		stridePixels = size_.width();
 		break;
 	};
+
+	/*
+	 * Compute the stride factor for the vertex shader, to map the
+	 * horizontal texture coordinate range [0.0, 1.0] to the active portion
+	 * of the image.
+	 */
+	shaderProgram_.setUniformValue(textureUniformStrideFactor_,
+				       static_cast<float>(size_.width() - 1) /
+				       (stridePixels - 1));
 }
 
 void ViewFinderGL::paintGL()
diff --git a/src/qcam/viewfinder_gl.h b/src/qcam/viewfinder_gl.h
index 2b2b1e86..37b1ddd0 100644
--- a/src/qcam/viewfinder_gl.h
+++ b/src/qcam/viewfinder_gl.h
@@ -97,6 +97,7 @@ private:
 
 	/* Raw Bayer texture parameters */
 	GLuint textureUniformSize_;
+	GLuint textureUniformStrideFactor_;
 	GLuint textureUniformBayerFirstRed_;
 	QPointF firstRed_;