void mapRect()

in libs/screen/image.cpp [362:400]

• 33 lines of code
• 12 McCabe index (conditional complexity)

void mapRect(Image_ img, int x, int y, int w, int h, Buffer map) {
    if (w == 0 || h == 0 || x >= img->width() || y >= img->height())
        return;

    if (img->bpp() != 4 || map->length < 16)
        return;

    int x2 = x + w - 1;
    int y2 = y + h - 1;

    if (x2 < 0 || y2 < 0)
        return;

    img->clamp(&x2, &y2);
    img->clamp(&x, &y);
    w = x2 - x + 1;
    h = y2 - y + 1;

    img->makeWritable();

    auto bh = img->byteHeight();
    auto m = map->data;
    uint8_t *p = img->pix(x, y);
    while (w-- > 0) {
        auto ptr = p;
        unsigned shift = y & 1;
        for (int i = 0; i < h; i++) {
            if (shift) {
                *ptr = (m[*ptr >> 4] << 4) | (*ptr & 0x0f);
                ptr++;
                shift = 0;
            } else {
                *ptr = (m[*ptr & 0xf] & 0xf) | (*ptr & 0xf0);
                shift = 1;
            }
        }
        p += bh;
    }
}