Well, it was leftover sort of. I had originally created one QImageReader, passed that pointer to all tiles, and used it to keep multiple threads for reading from the same file at once because I was getting some errors from libjpeg, libpng, etc. This made me think that was the issue.

Presently I get no errors, the image just doesnt load and look correct.

Well, it was leftover sort of. I had originally created one QImageReader, passed that pointer to all tiles, and used it to keep multiple threads for reading from the same file at once because I was getting some errors from libjpeg, libpng, etc. This made me think that was the issue.

Presently I get no errors, the image just doesnt load and look correct.

Here is the full code from my first try - passing a pointer to the reader into each tile:

Header:

Qt Code: 
  1. class RasterTile : public Tile
  2. {
  3. public:
  4.     RasterTile (QImageReader *reader, int nBlocksX, int nBlocksY, int xoffset, int yoffset, int nXBlockSize, int nYBlockSize);
  5.  
  6. protected:
  7.     QImageReader *reader;
  8.     void paint(QPainter *painter, const QStyleOptionGraphicsItem *option,QWidget *widget);
  9.     QImage LoadTilePixmap();
  10. private:
  11.     mutable QMutex mutex;
  12. };
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Cpp:

Qt Code: 
  1. #include "rastertile.h"
  2.  
  3. RasterTile::RasterTile(QImageReader *reader, int nBlocksX, int nBlocksY, int xoffset, int yoffset, int nXBlockSize, int nYBlockSize)
  4.     : Tile(nBlocksX, nBlocksY, xoffset, yoffset, nXBlockSize, nYBlockSize)
  5. {
  6.         this->reader = reader;
  7.         connect(&watcher,SIGNAL(finished()),this,SLOT(updateSceneSlot()));
  8. }
  9.  
  10.  
  11. void RasterTile::paint(QPainter *painter, const QStyleOptionGraphicsItem *option,QWidget *widget)
  12. {
  13.     if(image.isNull())
  14.     {
  15.         TilePainter=painter;
  16.         TileOption=option;
  17.         TileWidget=widget;
  18.         future = QtConcurrent::run(this, &RasterTile::LoadTilePixmap);
  19.         watcher.setFuture(future);
  20.  
  21.     }else
  22.     {
  23.         QRectF imageRect = image.rect();
  24.         painter->drawImage(imageRect, image);
  25.     }
  26.  
  27. }
  28.  
  29. QImage RasterTile::LoadTilePixmap()
  30. {
  31.     QMutexLocker locker(&mutex);
  32.     QImage img(nBlockXSize, nBlockYSize, QImage::Format_RGB32);
  33.     QRect rect(tilePosX*nBlockXSize, tilePosY*nBlockYSize, nBlockXSize, nBlockYSize);
  34.     reader->setClipRect(rect);
  35.     reader->read(&img);
  36.     return img;
  37.  
  38. }
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How I am instantiating the classes:

Qt Code: 
  1. for(int i =0; i < nXBlocks; i++)
  2.     {
  3.         for(int j = 0; j < nYBlocks; j++)
  4.         {
  5.             RasterTile *ipi = new RasterTile(reader,nXBlocks, nYBlocks, i, j, nXBlockSize, nYBlockSize);
  6.  
  7.         }
  8.     }
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After this try, is when i started trying to make the mutex private, and then also passing in just the file name so each Tile could create it's own reader.

"image" is a QImage that gets set to the img from "LoadTilePixmap()" and is set in the Tile::updateSceneSlot()