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Editorial Team
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Asked: 2026-05-11T16:11:44+00:00

I have the code here working fine except that all the non-power of 2

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I have the code here working fine except that all the non-power of 2 images are flipped in the y direction. In the wxImageLoader file there is this loop which I believe is the culprit:

    for(int y=0; y<newHeight; y++)
    {
        for(int x=0; x<newWidth; x++)
        {

            if( x<(*imageWidth) && y<(*imageHeight) ){
                imageData[(x+y*newWidth)*bytesPerPixel+0]=
                bitmapData[( x+(rev_val-y)*(*imageWidth))*old_bytesPerPixel + 0];

                imageData[(x+y*newWidth)*bytesPerPixel+1]=
                    bitmapData[( x+(rev_val-y)*(*imageWidth))*old_bytesPerPixel + 1];

                imageData[(x+y*newWidth)*bytesPerPixel+2]=
                    bitmapData[( x+(rev_val-y)*(*imageWidth))*old_bytesPerPixel + 2];

                if(bytesPerPixel==4) imageData[(x+y*newWidth)*bytesPerPixel+3]=
                    alphaData[ x+(rev_val-y)*(*imageWidth) ];

            }
            else
            {

                imageData[(x+y*newWidth)*bytesPerPixel+0] = 0;
                imageData[(x+y*newWidth)*bytesPerPixel+1] = 0;
                imageData[(x+y*newWidth)*bytesPerPixel+2] = 0;
                if(bytesPerPixel==4) imageData[(x+y*newWidth)*bytesPerPixel+3] = 0;
            }

        }//next
    }//next

But I can’t figure out how to un-flip the images.

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1 Answer

  1. Editorial Team

    The correct for loop is:

    for(int y=0; y<newHeight; y++)
    {
        for(int x=0; x<newWidth; x++)
        {

            if( x<(*imageWidth) && y<(*imageHeight) ){
                imageData[(x+y*newWidth)*bytesPerPixel+0]=
                bitmapData[( x+y*(*imageWidth))*old_bytesPerPixel + 0];

                imageData[(x+y*newWidth)*bytesPerPixel+1]=
                    bitmapData[( x+y*(*imageWidth))*old_bytesPerPixel + 1];

                imageData[(x+y*newWidth)*bytesPerPixel+2]=
                    bitmapData[( x+y*(*imageWidth))*old_bytesPerPixel + 2];

                if(bytesPerPixel==4) imageData[(x+y*newWidth)*bytesPerPixel+3]=
                    alphaData[ x+y*(*imageWidth) ];

            }
            else
            {

                imageData[(x+y*newWidth)*bytesPerPixel+0] = 0;
                imageData[(x+y*newWidth)*bytesPerPixel+1] = 0;
                imageData[(x+y*newWidth)*bytesPerPixel+2] = 0;
                if(bytesPerPixel==4) imageData[(x+y*newWidth)*bytesPerPixel+3] = 0;
            }

        }//next
    }//next
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