Increasing the memory allocation for MacDraw Pro can cause screen updating to be slower.
This can happen under the following conditions:
-- The computer's monitor is set to 2-color
-- The document contains a pixmap (a color/grayscale bitmap)
Under these conditions, MacDraw Pro attempts to dither the pixmap on screen so that it isn't displayed as a solid black block. This is actually an intended feature of MacDraw Pro, and is what is happening during this delay.
Any of the following actions cause MacDraw Pro not to dither the pixmap, hence eliminate the delay:
1. Change the monitor setting so it isn't 2-color (not much help when on a PowerBook, but good to know when using a different Mac
2. Turn on Image Greeking in Preferences
3. Reduce the memory partition (as you've already discovered). MacDraw Pro will detect that it doesn't have enough extra memory to calculate the dithering, so it won't try.
4. If the scanned image is 2-color black and white, try resaving from your scanning software in a different format (TIFF or PICT). Many scanning programs, when saving a black and white scan as a PICT or TIFF file, do not save the file out as a true bitmap file (strictly black and white). Or, the application may save it as a bitmap in one format, but a pixmap to the other format. If the file were saved as a true bitmap file (not a pixmap), this would solve the problem, as MacDraw Pro will not attempt to dither a bitmap file.