Do gamma conversion manualy

Requesting sRGB capable framebuffer is unreliable

imagescrollareagl.cpp

@@ -87,9 +87,6 @@ ImageWidget::ImageWidget(Database *database, QWidget *parent) : QOpenGLWidget(pa
     });
 
     setMouseTracking(true);
-#ifdef COLOR_MANAGMENT
-    setTextureFormat(GL_SRGB8_ALPHA8);
-#endif
 }
 
 ImageWidget::~ImageWidget()
@@ -335,9 +332,6 @@ void ImageWidget::paintGL()
     }
     else
     {
-#ifdef COLOR_MANAGMENT
-        if(m_srgb)f->glEnable(GL_FRAMEBUFFER_SRGB);
-#endif
         m_vao->bind();
         m_image->bind(0);
         m_program->bind();
@@ -347,10 +341,10 @@ void ImageWidget::paintGL()
         m_program->setUniformValue("zoom", 1.0f/m_scale);
         m_program->setUniformValue("bw", m_bwImg);
         m_program->setUniformValue("invert", m_invert);
-        f->glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
 #ifdef COLOR_MANAGMENT
-        if(m_srgb)f->glDisable(GL_FRAMEBUFFER_SRGB);
+        m_program->setUniformValue("srgb", m_srgb);
 #endif
+        f->glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
     }
 
 }

loadrunable.cpp

@@ -406,7 +406,7 @@ void LoadRunable::run()
     {
         QImage img(m_file);
 #ifdef COLOR_MANAGMENT
-        if(img.colorSpace().isValid())
+        if(img.colorSpace().isValid() && img.colorSpace() != QColorSpace::SRgb)
             img.convertToColorSpace(QColorSpace::SRgb);
 #endif
 

main.cpp

@@ -15,9 +15,6 @@ int main(int argc, char *argv[])
     format.setMinorVersion(3);
     format.setOption(QSurfaceFormat::DebugContext);
     format.setProfile(QSurfaceFormat::OpenGLContextProfile::CoreProfile);
-#ifdef COLOR_MANAGMENT
-    format.setColorSpace(QSurfaceFormat::sRGBColorSpace);
-#endif
     QSurfaceFormat::setDefaultFormat(format);
 
     QApplication a(argc, argv);

shaders/image.frag

@@ -4,9 +4,17 @@ uniform sampler2D qt_Texture0;
 uniform vec3 mtf_param;
 uniform bool bw;
 uniform bool invert;
+uniform bool srgb;
 in vec2 qt_TexCoord0;
 out vec4 color;
 
+vec3 Linear2sRGB(vec3 color)
+{
+    return mix(12.92 * color.rgb,
+               1.055 * pow(color, vec3(1.0 / 2.4)) - 0.055,
+               greaterThan(color, vec3(0.0031308)));
+}
+
 vec4 MTF(vec4 x, vec3 m)
 {
     x = (x - m.x) / (m.z - m.x);
@@ -22,6 +30,8 @@ void main(void)
 
     if(invert)color = vec4(1.0) - color;
 
+    if(srgb)color.rgb = Linear2sRGB(color.rgb);
+
     if(any(lessThan(qt_TexCoord0, vec2(0.0))) || any(greaterThan(qt_TexCoord0, vec2(1.0))))
         color = vec4(0.0, 0.0, 0.0, 1.0);