+ inline unsigned char *start(void) {
+ return flipped ? pixels + (height - 1)*width*4 : pixels;
+ }
+
+ inline unsigned char *end(void) {
+ return flipped ? pixels - width*4 : pixels + height*width*4;
+ }
+
+ inline signed stride(void) const {
+ return flipped ? -width*4 : width*4;
+ }
+