wbhart, for CGA mode no sence to draw a sprite by columns instead of rows. Calculating next column via INC adr is cheaper instead of row.

And I don't see how one can move down a column instead of across a row without incurring additional costs due to the odd/even layout of screen lines in CGA memory. At least for this problem, we have a solution. This can be done as in my code above. Calculate whether the first line of the sprite is …

So, this algorithm is a good starting point. Although it can be slightly improved, since we have one free register. But it has some drawback. It outputs a sprite that is a multiple of a byte, not a pixel. I don't think we should convert bytes representation to pixels, but we should add another …

Dear wbhart ! Thanks for your reply. We can't do without a shift anyway, since we want to output positions that are not multiples of four. I developed the subroutine that I roughly wanted. And it can be a starting point for learning. Also I will certainly be very happy with your additions and …

We can make it even easier: If the first line is odd, GOTO 1$ 0$: Draw an even line If there are no more lines, exit Switch to the next odd line 1$: Draw an odd line If there are no more lines, exit Switch to the next even line GOTO 0$ This is a fast and good algorithm. This way, there is really no …

I came up with two tricks for the analog of "putimage" subroutine: 1. In the game Battle City for CGA, I saw a subroutine that is approximately similar to what I need. But that subroutine uses an internal buffer for bit-shifting the line. http://www.balagurov.com/software/tank How to do without a …

Dear wbhart, I'm very impressed with your achievements at the quick drawing of pixel graphic and sprites, especially clipping off the outside of the screen! Especially on such a slow machine. And I thought: wbhart is the person who can only help me. I want to port the game from ZX Spectrum to DOS/ …