[comp.sys.amiga] BltBitMap vs. CopyBlit

nevets@ihlpm.ATT.COM (Steven R Ringwood) (08/11/87)

I found an example of program which reads in lo-res IFF files and
displays them on the screen.

It uses the function CopyBlit to transfer the image to the
screen.  I tried modifying it to use BltBitMap instead.
After making the changes, no pitcure, the color map changed, but the
picture hits the bit bucket.

As I understand it these two functions are basically the same,
only CopyBlit takes pointers to RasterPorts while BltBitMap takes
pointers to BitMaps.

From memory, the arguments where

	CopyBlit(	&src->rasterport, 0L, 0L,
			&dst->rasterport, &dst.x, &dst.y,
			&dst.h, &dst.w, 0xc0);
			
This was working fine.  I tried changing it to

	BltBitMap(	&src->rasterport.bitmap, 0L, 0L,
			&dst->rasterport.bitmap, &dst.x, &dst.y,
			&dst.h, &dst.w, 0xc0, 0xff, NULL);
			
As i understand it the second to last argument controls which
bit planes are involved in the transfer ( which is why i want to
use BltBitMap instead of CopyBlit), and the last argument
is a pointer to tempory storage to be used when the src and
dst bitmaps overlap.  In this case they are completely seperate,
ones off screen (src) and the other one is on screen (dst).

Can anyone give me any help on what i'm missing?

				Thanks much
				Steve Ringwood
				ihnp4!ihlpm!nevets