1、32位图数据转换成24位位图数据：
unsigned char* RGB32TO24(unsigned char* src, int width, int height) { uint8_t* data = NULL; uint32_t src_row_bytes; uint32_t dst_row_bytes; uint32_t off; int i,j; uint32_t* ptr; uint8_t* img; uint32_t color; int pad; src_row_bytes = width << 2; dst_row_bytes = (width * 3 + 3) & ~3; pad = dst_row_bytes - width * 3; data = (uint8_t*)malloc(dst_row_bytes * height); if (!data) { return NULL; } off = (height - 1) * dst_row_bytes; ptr = (uint32_t*)src; for(i = 0; i < height; i++) { img = data + off; for (j = 0; j < width; j++) { color = *ptr++; *img++ = color & 0x000000FF; *img++ = (color >> 8) & 0x000000FF; *img++ = (color >> 16) & 0x000000FF; } off -= dst_row_bytes; } return data; }src_row_bytes为32位位图一行所占的内存空间大小，一个像素占据4个字节的数据，所以不用考虑内存对齐问题；dst_row_bytes为24位位图一行所占据内存空间，一个像素3个字节，所以这里需要考虑内存字节对齐问题，dst_row_bytes需要是容纳width*3的最小的4的倍数。
2、24位位图转换成32位位图：
unsigned char* RGB24TO32(unsigned char* src, int width, int height) { uint8_t* data; int row_bytes; int i,j; uint8_t* dst; uint8_t* ptr; int src_pad; uint32_t off; row_bytes = (width * 3 + 3) & ~3; data = (uint8_t*)malloc(width * 4 * height); if(!data) return NULL; off = (height - 1)*row_bytes; dst = data; for(i = 0; i < height;i++) { ptr = src + off; for(j = 0; j < width; j++) { *dst++ = *ptr++; *dst++ = *ptr++; *dst++ = *ptr++; *dst++ = 0; } off -= row_bytes; } return data; }row_bytes跟上文一样，不赘述。
