+ return main_chain_lq.chain, prepare
+ end
+end
+
+function place_rectangle(resample_effect, resize_effect, padding_effect, x0, y0, x1, y1, screen_width, screen_height, input_width, input_height)
+ local srcx0 = 0.0
+ local srcx1 = 1.0
+ local srcy0 = 0.0
+ local srcy1 = 1.0
+
+ -- Cull.
+ if x0 > screen_width or x1 < 0.0 or y0 > screen_height or y1 < 0.0 then
+ resample_effect:set_int("width", 1)
+ resample_effect:set_int("height", 1)
+ resample_effect:set_float("zoom_x", screen_width)
+ resample_effect:set_float("zoom_y", screen_height)
+ padding_effect:set_int("left", screen_width + 100)
+ padding_effect:set_int("top", screen_height + 100)
+ return
+ end
+
+ -- Clip.
+ if x0 < 0 then
+ srcx0 = -x0 / (x1 - x0)
+ x0 = 0
+ end
+ if y0 < 0 then
+ srcy0 = -y0 / (y1 - y0)
+ y0 = 0
+ end
+ if x1 > screen_width then
+ srcx1 = (screen_width - x0) / (x1 - x0)
+ x1 = screen_width
+ end
+ if y1 > screen_height then
+ srcy1 = (screen_height - y0) / (y1 - y0)
+ y1 = screen_height
+ end
+
+ 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", srcx0 * input_width - x_subpixel_offset / zoom_x)
+ resample_effect:set_float("top", srcy0 * input_height - 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))