Correctly render BW image

image.frag

@@ -5,10 +5,12 @@ varying vec2 qt_TexCoord0;
 uniform vec2 scale;
 uniform float a;
 uniform int stretch;
+uniform bool bw;
 
 void main(void)
 {
     vec4 color = texture2D(qt_Texture0, qt_TexCoord0);
+    if(bw)color = color.rrra;
     color = color*scale.x + scale.y;
     max(color, vec4(0.0f));
 

imagescrollareagl.cpp

@@ -64,6 +64,7 @@ void ImageWidget::setImage(RawImage *image)
         break;
     }
     m_image->generateMipMaps();
+    m_bwImg = true;
     update();
 }
 
@@ -79,6 +80,7 @@ void ImageWidget::setImage(const QPixmap &pixmap)
     m_image->setMinMagFilters(QOpenGLTexture::LinearMipMapLinear, QOpenGLTexture::Linear);
     m_image->setWrapMode(QOpenGLTexture::ClampToBorder);
     m_image->setBorderColor(0, 0, 0, 0);
+    m_bwImg = false;
     update();
 }
 
@@ -167,6 +169,7 @@ void ImageWidget::paintGL()
     m_program->setUniformValue("stretch", m_stretch);
     m_program->setUniformValue("a", m_param);
     m_program->setUniformValue("zoom", 1.0f/m_scale);
+    m_program->setUniformValue("bw", m_bwImg);
 
     m_image->bind(0);
     f->glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

imagescrollareagl.h

@@ -40,6 +40,7 @@ class ImageWidget : public QOpenGLWidget
     float m_scale;
     float m_param;
     bool m_blockRepaint;
+    bool m_bwImg;
 public:
     explicit ImageWidget(QWidget *parent = nullptr);
     ~ImageWidget();