add mention to get_pixels

Author: villares

py5_docs/Reference/api_en/Sketch_copy.txt

@@ -27,6 +27,8 @@ Copies a region of pixels from the display window to another area of the display
 
 This function ignores [](sketch_image_mode).
 
+If you want to create a new image with the contents of a rectangular region of the sketch, check out [](sketch_get_pixels) where x, y, w, h, are the position and dimensions of the area to be copied. It will return a `Py5Image` object.
+
 @@ example
 image = Sketch_copy_0.png