- // Clip. (TODO: Clip on upper/left sides, too.)
- if (x1 > 1280.0) {
- srcx1 = (1280.0 - x0) / (x1 - x0);
- x1 = 1280.0;
- }
- if (y1 > 720.0) {
- srcy1 = (720.0 - y0) / (y1 - y0);
- y1 = 720.0;
- }
-
- float x_subpixel_offset = x0 - floor(x0);
- float y_subpixel_offset = y0 - floor(y0);
-
- // Resampling must be to an integral number of pixels. Round up,
- // and then add an extra pixel so we have some leeway for the border.
- int width = int(ceil(x1 - x0)) + 1;
- int height = int(ceil(y1 - y0)) + 1;
- CHECK(resample_effect->set_int("width", width));
- CHECK(resample_effect->set_int("height", height));
-
- // Correct the discrepancy with zoom. (This will leave a small
- // excess edge of pixels and subpixels, which we'll correct for soon.)
- float zoom_x = (x1 - x0) / (width * (srcx1 - srcx0));
- float zoom_y = (y1 - y0) / (height * (srcy1 - srcy0));
- CHECK(resample_effect->set_float("zoom_x", zoom_x));
- CHECK(resample_effect->set_float("zoom_y", zoom_y));
- CHECK(resample_effect->set_float("zoom_center_x", 0.0f));
- CHECK(resample_effect->set_float("zoom_center_y", 0.0f));
-
- // Padding must also be to a whole-pixel offset.
- CHECK(padding_effect->set_int("left", floor(x0)));
- CHECK(padding_effect->set_int("top", floor(y0)));
-
- // Correct _that_ discrepancy by subpixel offset in the resampling.
- CHECK(resample_effect->set_float("left", -x_subpixel_offset / zoom_x));
- CHECK(resample_effect->set_float("top", -y_subpixel_offset / zoom_y));
-
- // Finally, adjust the border so it is exactly where we want it.
- CHECK(padding_effect->set_float("border_offset_left", x_subpixel_offset));
- CHECK(padding_effect->set_float("border_offset_right", x1 - (floor(x0) + width)));
- CHECK(padding_effect->set_float("border_offset_top", y_subpixel_offset));
- CHECK(padding_effect->set_float("border_offset_bottom", y1 - (floor(y0) + height)));
-}
-