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authorLaurent Pinchart <laurent.pinchart@ideasonboard.com>2024-09-09 16:13:20 +0300
committerLaurent Pinchart <laurent.pinchart@ideasonboard.com>2024-09-11 18:24:51 +0300
commite6441ec4f4a68518c3f01c753ef179226f56ebfc (patch)
treed7eb078494b0861c8a62cc49ec93b273e6c37fb3
parent583901a714d50adf28f248ccdad5867050979058 (diff)
qcam: viewfinder_gl: Render image centered in letterbox
Mimic the letterbox behaviour of the Qt viewfinder by rendering the image centered. This is done by adding a projection matrix to the vertex shader to scale the rendered rectangle. Another option would have been to keep using glViewport() (which would have needed to be moved to paintGL(), as Qt resets the viewport to span the full widget before calling). Hidpi displays would then need special handling of the device pixel ratio, which is done automatically by Qt when it sets the default viewport. Using a projection matrix avoids this complication. Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Tested-by: Kieran Bingham <kieran.bingham@ideasonboard.com> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
-rw-r--r--src/apps/qcam/assets/shader/bayer_8.vert4
-rw-r--r--src/apps/qcam/assets/shader/identity.vert3
-rw-r--r--src/apps/qcam/viewfinder_gl.cpp31
-rw-r--r--src/apps/qcam/viewfinder_gl.h2
4 files changed, 26 insertions, 14 deletions
diff --git a/src/apps/qcam/assets/shader/bayer_8.vert b/src/apps/qcam/assets/shader/bayer_8.vert
index 3695a5e9..fb5109ee 100644
--- a/src/apps/qcam/assets/shader/bayer_8.vert
+++ b/src/apps/qcam/assets/shader/bayer_8.vert
@@ -19,6 +19,8 @@ Copyright (C) 2021, Linaro
attribute vec4 vertexIn;
attribute vec2 textureIn;
+uniform mat4 proj_matrix;
+
uniform vec2 tex_size; /* The texture size in pixels */
uniform vec2 tex_step;
@@ -47,5 +49,5 @@ void main(void) {
yCoord = center.y + vec4(-2.0 * tex_step.y,
-tex_step.y, tex_step.y, 2.0 * tex_step.y);
- gl_Position = vertexIn;
+ gl_Position = proj_matrix * vertexIn;
}
diff --git a/src/apps/qcam/assets/shader/identity.vert b/src/apps/qcam/assets/shader/identity.vert
index 12c41377..907e8741 100644
--- a/src/apps/qcam/assets/shader/identity.vert
+++ b/src/apps/qcam/assets/shader/identity.vert
@@ -9,10 +9,11 @@ attribute vec4 vertexIn;
attribute vec2 textureIn;
varying vec2 textureOut;
+uniform mat4 proj_matrix;
uniform float stride_factor;
void main(void)
{
- gl_Position = vertexIn;
+ gl_Position = proj_matrix * vertexIn;
textureOut = vec2(textureIn.x * stride_factor, textureIn.y);
}
diff --git a/src/apps/qcam/viewfinder_gl.cpp b/src/apps/qcam/viewfinder_gl.cpp
index b2096faf..f31956ff 100644
--- a/src/apps/qcam/viewfinder_gl.cpp
+++ b/src/apps/qcam/viewfinder_gl.cpp
@@ -12,6 +12,7 @@
#include <QByteArray>
#include <QFile>
#include <QImage>
+#include <QMatrix4x4>
#include <QStringList>
#include <libcamera/formats.h>
@@ -464,6 +465,7 @@ bool ViewFinderGL::createFragmentShader()
vertexBuffer_.release();
+ projMatrixUniform_ = shaderProgram_.uniformLocation("proj_matrix");
textureUniformY_ = shaderProgram_.uniformLocation("tex_y");
textureUniformU_ = shaderProgram_.uniformLocation("tex_u");
textureUniformV_ = shaderProgram_.uniformLocation("tex_v");
@@ -509,7 +511,7 @@ void ViewFinderGL::initializeGL()
glEnable(GL_TEXTURE_2D);
glDisable(GL_DEPTH_TEST);
- static const GLfloat coordinates[2][4][2]{
+ const GLfloat coordinates[2][4][2]{
{
/* Vertex coordinates */
{ -1.0f, -1.0f },
@@ -801,6 +803,17 @@ void ViewFinderGL::doRender()
shaderProgram_.setUniformValue(textureUniformStrideFactor_,
static_cast<float>(size_.width() - 1) /
(stridePixels - 1));
+
+ /*
+ * Place the viewfinder in the centre of the widget, preserving the
+ * aspect ratio of the image.
+ */
+ QMatrix4x4 projMatrix;
+ QSizeF scaledSize = size_.scaled(size(), Qt::KeepAspectRatio);
+ projMatrix.scale(scaledSize.width() / size().width(),
+ scaledSize.height() / size().height());
+
+ shaderProgram_.setUniformValue(projMatrixUniform_, projMatrix);
}
void ViewFinderGL::paintGL()
@@ -818,18 +831,14 @@ void ViewFinderGL::paintGL()
close();
}
- if (image_) {
- glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
- glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+ if (!image_)
+ return;
- doRender();
- glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
- }
-}
+ glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
+ glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
-void ViewFinderGL::resizeGL(int w, int h)
-{
- glViewport(0, 0, w, h);
+ doRender();
+ glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
}
QSize ViewFinderGL::sizeHint() const
diff --git a/src/apps/qcam/viewfinder_gl.h b/src/apps/qcam/viewfinder_gl.h
index 23744b41..23c657bc 100644
--- a/src/apps/qcam/viewfinder_gl.h
+++ b/src/apps/qcam/viewfinder_gl.h
@@ -51,7 +51,6 @@ Q_SIGNALS:
protected:
void initializeGL() override;
void paintGL() override;
- void resizeGL(int w, int h) override;
QSize sizeHint() const override;
private:
@@ -88,6 +87,7 @@ private:
/* Common texture parameters */
GLuint textureMinMagFilters_;
+ GLuint projMatrixUniform_;
/* YUV texture parameters */
GLuint textureUniformU_;