(a)
if ((yy >= filterRect->bottom) || (yy < filterRect->top) ||
(xx < filterRect->left) || (xx >= filterRect->right))
continue; // (x,y) outside rectangle
(b)
bool leaveItAlone = false;
if (maskPixel != NULL && !gParams->ignoreSelection &&
!(*(maskPixel + pixelOffset)))
leaveItAlone = true;
if (!leaveItAlone) {}