strange question & for experts only...

[DanBoris]

As you suspected the problem with this is how much time Maria has to get the data into the scanline. For each scanline you have 456 Maria cycles to generate the scanline.

 

Each byte you transfer to the scanline requires 3 cycles. If you used the 160x2 mode which would give you 160 pixels across in 4 colors, it would require 40 bytes to cover the whole scanline. So 40 * 3 = 120 + 8 (for the header) = 128 cycles per line. So you could only 3 different graphic lines on one scanline.

 

Dan

[Heaven/TQA]

but dan. when i want to have a smaller logo on the screen, f.e. "SENSO" or "TQA" it should be then possible...

 

f.e. 64x32x24 logo

 

64/4=16 bytes*3+8=56

 

456 div 56=8 tata... correct?

 

and even 3x overlaying gfx gives us 12 colors or 9 colors if background is always

the same color... much more than standard "antic e" 160x2x4

 

hve

 

ps. the mathematical problem is gone... because the software can set the pixles while converting free, right? MARIA has 24 different independend color registers... so no optimasations & color reduction has to be calculated. more difficult of course would be to render a 256 color picture down to HVE-format...

[Heaven/TQA]

the correct link to HIP-format

 

http://www.s-direktnet.de/homepages/k_nadj/hip.html

[Heaven/TQA]

re atari 7800...

 

coming from atari computers i had the idea if someone could program a gfx converter tool which uses full 24 colors for a hires gfx. it must be possible

 

similar tools are existing on gameboy color or even atari (HIP http://www.s-direktnet.de/homepages/k_nadj/hip.html)

 

idea is:

 

put all 8 different hires gfx lines on the same scanline each with different reference to color registers. the BMP2HVE (HVE is the new format... ;=)) routine sets the pixels correct as much the algorithm could do...

 

question:

 

1) do you think this is possible?

2) is the MARIA capable to display so much information at the time?

3) you has the mathematical knowledge to do this? (i haven't....)

 

think about it...

 

HVE

[calamari]

quote

more difficult of course would be to render a 256 color picture down to HVE-format...

 

You may want to check out Paint Shop Pro. Since there are more than 16 colors, you could use it to dither the image from 256 colors to the "best" 24 colors. If the 24 Atari colors are fixed, then you could create a custom palette, and load that on the image. Or you could write a dithering program yourself Just spread any color error down and to the right for each pixel.

 

calamari

[Eckhard Stolberg]

There already is the 160x4 mode which provides 12 colours for the graphics. (Colours 0, 4, 8 and 12 are transparent.) But since the 7800 has 24 colour registers, you can select between two sets of 12 colours each in this screen mode. The DMA isn't fast enough to cover a full line with both palettes, but about 120 pixels in 24 colours should be possible without any tricks.

 

But when you asked about hires graphics, I thought you meant a 320 pixel mode. For those modes it would be very difficult to squeeze out more colours, since you need to proceed more data, and because the colour setection is very limited in all 320 pixel modes.

 

 

Ciao, Eckhard Stolberg

[Heaven/TQA]

re hires mode

 

when i was talking about hires i ment 160x modes...as coming from atari 320x modes are always lacking of colors... and strangly human eyes like to have more colors even when it is a lower resolution...

 

160x4 this mode i havent understood to be honest. the bit selection is in my opinion so strange that it seems to me there is no right freedom to choice the colors... and the overlaying 160x2 mode for 24 free colors seems more practical right now

 

but maybe someone can proove me right conc. 160x4... 12 colors free or not?

 

hve

[Eckhard Stolberg]

The 160x4 mode is pretty simple actually. The 7800 has 8 palettes with 3 usable colours each (colour 0 in each palette is transparent or background). In 160x4 mode you are grouping palettes 0-3 and 4-7 together. Usually the display list entry selects one of the 8 palettes for your object. In this mode only the highest bit is used to select one of the two palette groups.

 

Each byte of graphics data specifies two pixels. The low-nibble of the byte lets you select one of the 4 palettes for either pixel, and the high-nibble selects the colour in the chosen palette. The left half of the nibbles is for the left pixel, and the right half of the nibbles is for the right pixel.

 

So lets say you have a graphics data byte of %01_10_00_11. For the left pixel that would select palette %00 and colour %01. If you had chosen the first palette group in the display list entry, this would mean that the left pixel would use the colour from P0C1. Likewise the right pixel would use the colour from P3C2. If the display list entry would point to the second palette group, the colours would be P4C1 and P7C2.

 

I hope this makes it a bit more understandable for you.

 

 

Ciao, Eckhard Stolberg