Software Technology Tips

uint8* dstPtr = (uint8*) dstData;

uint8* srcPtr = (uint8*) srcData;

int32 bytesPerRow = CGBitmapContextGetBytesPerRow(context); 

int32 planeBits = CGBitmapContextGetBitsPerComponent(context);

float  width  = CGImageGetWidth(srcImage);

float  height = CGImageGetHeight(srcImage);

short totalRows = height;

short totalColumns = width;

short totalPlanes = 4;       //No of planes per pixel i.e. R, G, B & alpha.

short planeBytes = planeBits/8;

short loopRows, loopColumns, plane;

 for(loopRows = 0; loopRows < totalRows; loopRows++)

{

srcPtr = (uint8 *) srcData + (loopRows * bytesPerRow);

dstPtr = (uint8 *) dstData + (loopRows * bytesPerRow);

for(loopColumns = 0; loopColumns < totalColumns; loopColumns++)

{          

for (plane = 0; plane < totalPlanes; plane++)

{                

switch (plane)

{

case 0:

case 1:

case 2:

srcByte = srcPtr [plane * planeBytes];

dstByte = dstPtr[plane * planeBytes];

newSrcByte = (srcImageOpacity*srcByte)/100;

newDstByte = (dstImageOpacity*dstByte)/100;

dstPtr [plane * planeBytes] = newDstByte + newSrcByte;

break;

default:

break;

}

// copy the second byte also if there r two bytes per plane

if(planeBytes == 2)

dstPtr [plane * planeBytes + 1] = srcPtr [plane * planeBytes + 1];

}

dstPtr += totalPlanes * planeBytes;

        srcPtr += totalPlanes * planeBytes;

}

}