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bitmap problem

Started by PPCThug Mar 4, 2003 at 9:06 PM 5 replies 300+ views

Original Post

Mar 4, 2003 at 9:06 PM

I made a program to load a bit map with text that reads "new game", but when it runs the bit map is doubled like "new game new game" and there is garbage underneath it, like dots and lines of random color. if this is not enough info I will post the source code, but I hope that will not be necessary. heres the 24 to 16 bit convesion, since the bit map is 24 bit it might be the problem

  

 
    for (int index_y = 0; index_y < bitmap.bitmapinfoheader.biHeight; index_y++)
        {
        for (int index_x = 0; index_x < bitmap.bitmapinfoheader.biWidth; index_x++)
                {
                // get BGR values, note the scaling down of the channels, so that they

                // fit into the 5.6.5 format

                UCHAR blue  = (bitmap.buffer[index_y*bitmap.bitmapinfoheader.biWidth*3 + index_x*3 + 0]) >> 3,
                green = (bitmap.buffer[index_y*bitmap.bitmapinfoheader.biWidth*3 + index_x*3 + 1]) >> 3,
                red   = (bitmap.buffer[index_y*bitmap.bitmapinfoheader.biWidth*3 + index_x*3 + 2]) >> 3;
                
                // this builds a 16 bit color value in 5.6.5 format (green dominant mode)

                USHORT pixel = _RGB16BIT565(red,green,blue);
                
                // write the pixel

                image_buffer[index_x + (index_y*ddsd.lPitch >> 1)] = pixel;
                
                } // end for index_x         

                        
        } // end for index_y

Bloodshed Dev-C++ 4.01 DX 8.0a DX SDK 6.1 win98 #define WIN32_LEAN_AND_MEAN the Particle Projection Cannon fires a shimmering blue bolt, much like a cross between lightning and a sine wave that ripples along its path.

Hoser

Mar 4, 2003 at 9:47 PM

One problem that I see is that you aren''t taking into account the fact that each line of a bitmap is a multiple of 4 bytes. For example, say you had a 24 bit RGB bitmap that was 5 pixels wide. Each line of the bitmap only requires 15 bytes...however, an extra byte will be padded onto the end of each line so that it is 16 bytes (multiple of 4 bytes).

This will cause all kinds of problems in your conversion from 24 bit to 16 bit...all your memory offsets will be wrong.

PPCThug

Mar 5, 2003 at 1:09 AM

1: If you don''t like the code talk Andre LaMothe, he wrote it.
2: the bitmap whas 160 pixels wide so I don''t think that whas the problem, tho I will try to fix it. (why multiples of 4 bytes?)