Workaround in AMD OpenGL driver bug

AMD OpenGL driver on Windows doesn't generate mipmaps for sRGB textures
correctly

imagescrollareagl.cpp

@@ -11,6 +11,7 @@
 #include <QCoreApplication>
 #include <QPainter>
 #include <QFileInfo>
+#include <cmath>
 
 struct RawImageType
 {
@@ -36,6 +37,8 @@ const RawImageType rawImageTypes[] = {
     {QOpenGLTexture::RGB, QOpenGLTexture::RGB32F, QOpenGLTexture::Float32, false}
 };
 
+static bool MANUAL_MIPMAP_GEN = false;
+
 void setScrollRange(QScrollBar *scrollBar, int newRange)
 {
     int page = scrollBar->pageStep();
@@ -105,8 +108,11 @@ void ImageWidget::setImage(std::shared_ptr<RawImage> image, int index)
     m_currentImg = index;
 
     const RawImageType &rawImageType = rawImageTypes[image->type()];
+    m_srgb = rawImageType.textureFormat == QOpenGLTexture::SRGB8 || rawImageType.textureFormat == QOpenGLTexture::SRGB8_Alpha8;
+    m_bwImg = rawImageType.bw;
 
     m_image->destroy();
+    m_image->setAutoMipMapGenerationEnabled(false);
     m_image->setFormat(rawImageType.textureFormat);
     m_image->setSize(image->width(), image->height());
     m_image->setMipLevels([&](){ int c = 0; int s = std::min(m_imgWidth, m_imgHeight); while(s>>=1)c++; return c; }());
@@ -115,10 +121,42 @@ void ImageWidget::setImage(std::shared_ptr<RawImage> image, int index)
     m_image->setWrapMode(QOpenGLTexture::ClampToEdge);
     m_image->setBorderColor(0, 0, 0, 0);
     m_image->setData(0, rawImageType.pixelFormat, rawImageType.dataType, (const void*)image->data(), m_transferOptions.get());
+
+    auto sRGB_linear = [](cv::Point3f &pixel, const int *pos)
+    {
+        pixel.x = pixel.x <= 0.04045f ? pixel.x / 12.92f : std::pow((pixel.x + 0.055) / 1.055f, 2.4f);
+        pixel.y = pixel.y <= 0.04045f ? pixel.y / 12.92f : std::pow((pixel.y + 0.055) / 1.055f, 2.4f);
+        pixel.z = pixel.z <= 0.04045f ? pixel.z / 12.92f : std::pow((pixel.z + 0.055) / 1.055f, 2.4f);
+    };
+
+    auto linear_sRGB = [](cv::Point3f &pixel, const int *pos)
+    {
+        pixel.x = pixel.x <= 0.0031308f ? pixel.x * 12.92f : 1.055f * std::pow(pixel.x , 1/2.4f) - 0.055f;
+        pixel.y = pixel.y <= 0.0031308f ? pixel.y * 12.92f : 1.055f * std::pow(pixel.y , 1/2.4f) - 0.055f;
+        pixel.z = pixel.z <= 0.0031308f ? pixel.z * 12.92f : 1.055f * std::pow(pixel.z , 1/2.4f) - 0.055f;
+    };
+
+    //AMD OpenGL driver on Windows doesn't generate mipmaps for sRGB textures correctly
+    if(m_srgb && MANUAL_MIPMAP_GEN)
+    {
+        cv::Mat img = image->mat();
+        img.convertTo(img, CV_32FC3, 1/255.0);
+        img.forEach<cv::Point3f>(sRGB_linear);
+        cv::Size size(img.cols, img.rows);
+        for(int i=1; i<m_image->mipLevels(); i++)
+        {
+            cv::Mat mip;
+            size /= 2;
+            cv::resize(img, mip, size);
+            mip.copyTo(img);
+            mip.forEach<cv::Point3f>(linear_sRGB);
+            mip.convertTo(mip, CV_8UC3, 255);
+            m_image->setData(i, rawImageType.pixelFormat, rawImageType.dataType, (const void*)mip.ptr(), m_transferOptions.get());
+        }
+    }
+    else m_image->generateMipMaps();
+
     m_image->setLevelOfDetailRange(m_superpixel ? 1 : 0, m_image->mipMaxLevel());
-    m_image->generateMipMaps();
-    m_bwImg = rawImageType.bw;
-    m_srgb = rawImageType.textureFormat == QOpenGLTexture::SRGB8 || rawImageType.textureFormat == QOpenGLTexture::SRGB8_Alpha8;
     update();
 }
 
@@ -351,6 +389,8 @@ void ImageWidget::initializeGL()
     qDebug() << (char*)f->glGetString(GL_RENDERER);
     qDebug() << (char*)f->glGetString(GL_VERSION);
 
+    MANUAL_MIPMAP_GEN = QString((const char*)f->glGetString(GL_VENDOR)).startsWith("ATI Technologies Inc", Qt::CaseInsensitive);
+
     qDebug() << context()->format();
 
     // each vertex is  x,y 2D position and s,t texture coordinates