Faster way to copy a region from a bitmap in C

Question

I am using the following way to copy a region from a bitmap in rgb565 pixel format:

void bmpcpy(size_t left, size_t top, size_t right, size_t bottom) {
    size_t index = 0;
    
    do {
        do {
            bmpCopy[index] = bmpSrc[(top * BMP_WIDTH) + left];
            index++;
        } while (++left < right);
    } while (++top < bottom);
}

Is there a faster way to do the copy?

Answer 1

There might be faster ways using memcpy or accelerated graphics APIs, but first notice that your code is flawed:

• bmpCopy and bmpSrc are not defined, it is unlikely they should be global variables.
• bmpCopy is assumed to have a straddle value of right - left , not necessarily correct because of alignment constraints.
• left is not reset for each row.
• the width and height of the region are assumed to be non zero.

Depending on the type of bmpSrc , the parity and amplitude of width and the alignment of the source and destination pointers, it might be more efficient to copy multiple pixels at a time using a larger type.