- local x_subpixel_offset = x0 - math.floor(x0)
- local y_subpixel_offset = y0 - math.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.
- local width = math.ceil(x1 - x0) + 1
- local height = math.ceil(y1 - y0) + 1
- resample_effect:set_int("width", width)
- 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.)
- local zoom_x = (x1 - x0) / (width * (srcx1 - srcx0))
- local zoom_y = (y1 - y0) / (height * (srcy1 - srcy0))
- resample_effect:set_float("zoom_x", zoom_x)
- resample_effect:set_float("zoom_y", zoom_y)
- resample_effect:set_float("zoom_center_x", 0.0)
- resample_effect:set_float("zoom_center_y", 0.0)
-
- -- Padding must also be to a whole-pixel offset.
- padding_effect:set_int("left", math.floor(x0))
- padding_effect:set_int("top", math.floor(y0))
-
- -- Correct _that_ discrepancy by subpixel offset in the resampling.
- resample_effect:set_float("left", -x_subpixel_offset / zoom_x)
- resample_effect:set_float("top", -y_subpixel_offset / zoom_y)
-
- -- Finally, adjust the border so it is exactly where we want it.
- padding_effect:set_float("border_offset_left", x_subpixel_offset)
- padding_effect:set_float("border_offset_right", x1 - (math.floor(x0) + width))
- padding_effect:set_float("border_offset_top", y_subpixel_offset)
- padding_effect:set_float("border_offset_bottom", y1 - (math.floor(y0) + height))
+ if resample_effect ~= nil then
+ -- High-quality resampling.
+ local x_subpixel_offset = x0 - math.floor(x0)
+ local y_subpixel_offset = y0 - math.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.
+ local width = math.ceil(x1 - x0) + 1
+ local height = math.ceil(y1 - y0) + 1
+ resample_effect:set_int("width", width)
+ 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.)
+ local zoom_x = (x1 - x0) / (width * (srcx1 - srcx0))
+ local zoom_y = (y1 - y0) / (height * (srcy1 - srcy0))
+ resample_effect:set_float("zoom_x", zoom_x)
+ resample_effect:set_float("zoom_y", zoom_y)
+ resample_effect:set_float("zoom_center_x", 0.0)
+ resample_effect:set_float("zoom_center_y", 0.0)
+
+ -- Padding must also be to a whole-pixel offset.
+ padding_effect:set_int("left", math.floor(x0))
+ padding_effect:set_int("top", math.floor(y0))
+
+ -- Correct _that_ discrepancy by subpixel offset in the resampling.
+ resample_effect:set_float("left", -x_subpixel_offset / zoom_x)
+ resample_effect:set_float("top", -y_subpixel_offset / zoom_y)
+
+ -- Finally, adjust the border so it is exactly where we want it.
+ padding_effect:set_float("border_offset_left", x_subpixel_offset)
+ padding_effect:set_float("border_offset_right", x1 - (math.floor(x0) + width))
+ padding_effect:set_float("border_offset_top", y_subpixel_offset)
+ padding_effect:set_float("border_offset_bottom", y1 - (math.floor(y0) + height))
+ else
+ -- Lower-quality simple resizing.
+ local width = round(x1 - x0)
+ local height = round(y1 - y0)
+ resize_effect:set_int("width", width)
+ resize_effect:set_int("height", height)
+
+ -- Padding must also be to a whole-pixel offset.
+ padding_effect:set_int("left", math.floor(x0))
+ padding_effect:set_int("top", math.floor(y0))
+ end