BLuRry wrote:
Michael J. Mahon wrote:BLuRry wrote:I've been trying to figure out a way to render hires to a double-hires bitmap, but also taking into account the odd combinations of color frindges. See the following example paraphrased from Sather's book below: 1 hgr2:for a=1 to 3:read c:hcolor=c:read n:for b=1 to n: read x:hplot x,0 to x,191:next b,a:data 4,3,0,21,42,7,9,62,83,104,125,159,180,220,247,279,3,10,20,41,105,126,161,182,206,233,262,263 I know why it happens, I'm just trying to find the most efficient way to programatically explain this behavior. Any takers?I've never seen a program explain anything. ;-) If you mean how can you get exactly the same behavior from a DHR display that you see from an HGR display, that's pretty straightforward. The HGR display is a subset of the DHR display where each HGR pixel is represented by two DHR pixels. Instead of thinking about colors and "4-bit color pixels", just think about the video bits shifted out and the timing of their edges, as if it were a monochrome display. NTSC aliasing will take care of creating all the colors--and their fringes. For example, each of the seven low bits of an HGR line translates to two consecutive bits in the DHR line, and the high bit shifts their position in the DHR line by one DHR bit position.Yeah, I got that part -- but that doesn't quite cut it. If the hi-bit is set on one byte, but not the byte next to it, then only a half-pixel is shown. So there's more to it than just simple bit expansion. At byte boundaries when the hi-bit goes from hi to low, pixels get cut in half. So I'm trying to find the best logical representation of that behavior, hence represent (or "explain") the behavior algorithmically.
That behavior is obtained by setting only *one* of the bits in the DHR frame buffer, not two. If the amount "cut off" is not a whole bit time (70ns), then it will not be possible to create that "pixel fragment" using DHR. -michael NadaNet networking for Apple II computers! Home page: http://members.aol.com/MJMahon/ "The wastebasket is our most important design tool--and it's seriously underused."