Idea for math experts...

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By Manuel

Ascended (17312)

Manuel's picture

25-05-2007, 13:46

In that last picture, how many unique colors (RGB combinations) are visible? (Out of 512.)

By NYYRIKKI

Enlighted (5669)

NYYRIKKI's picture

30-05-2007, 19:33

Here is example of 512*480 picture:

msx.fi/temp/512_3.jpg

By Manuel

Ascended (17312)

Manuel's picture

30-05-2007, 22:50

Wow, so this is screen 7 with interlacing and overscan and the pallette trick? How many unique colours in this one??

By dvik

Prophet (2200)

dvik's picture

31-05-2007, 08:22

Yet another WOW ! The images look very good.

By NYYRIKKI

Enlighted (5669)

NYYRIKKI's picture

31-05-2007, 20:35

@DamageX

Ok... I've been trying to improve the graphic conversion routines, but pretty much without luck. It seems to me, that increasing the color selection "window size" does not have any practical meaning. Also I now understand better why you do the rastering before color selection. Smile

Only actual improvement that I managed to make was changeing the raster routine a bit more better for interlaced pictures by changeing Xalt=1-Xalt to Xalt=(h+v)and1 in BMP512.BAS

@manuel
Next time I promise to calculate the number of used colors for you, but not today. Tongue

Yet another picture (512*480)... they are just so cute Tongue
msx.fi/temp/512_4.jpg

By Sonic_aka_T

Enlighted (4130)

Sonic_aka_T's picture

31-05-2007, 21:22

Hmmm, that took me longer than it should have... Tongue

http://www.freedrive.com/files/j0pdm3f7ri80g/BMW.HAM
http://www.freedrive.com/files/j0pdm3f7ri80g/ViewMSX.exe

hope it woiks (also not sure if the links work...)

Maybe this works... http://www.freedrive.com/members/j0pdm3f7ri80g/

By Sonic_aka_T

Enlighted (4130)

Sonic_aka_T's picture

31-05-2007, 21:41

By DamageX

Master (217)

DamageX's picture

01-06-2007, 07:01

Also I now understand better why you do the rastering before color selection.
The main reason is that it seemed easier to code Smile Using the floyd-steinburg routine (like in the VDPENC thread) would probably be better overall. I think that "hamlab" on the Amiga can use it when converting from 24-bit to 12-bit and again after color reduction.
changeing Xalt=1-Xalt to Xalt=(h+v)and1 in BMP512.BAS
good idea! I can use that improvement in some other unrelated programs.
http://www.freedrive.com/files/j0pdm3f7ri80g/BMW.HAM
http://www.freedrive.com/files/j0pdm3f7ri80g/ViewMSX.exe

hope it woiks (also not sure if the links work...)
Nice :) and it even counts the total number of colors (=128 for this one)

By DamageX

Master (217)

DamageX's picture

01-06-2007, 07:03

oh BTW, how do you display more than 424 lines on the MSX? I wasn't aware of this trick

By turbor

Champion (454)

turbor's picture

01-06-2007, 14:53

It is called 'the overscan trick' it could be said that it is a 'feature' of the VDP Smile
The VDP has a bit that determines if it displays 192 or 212 lines for each frame.
Once this number is reached the VDP turns off the screen and goes into horizontal border behaviour.
The way it works seems to be that the vdp tests if linecount == 192 or linecount ==212, depending on that settings bit.

The trick is that you start telling the vdp that you're going to display 212 line, but somewhere between line 193 and 211 you change your mind and tell the vdp to check for 192 lines. The VDP will keep on counting lines and displaying them...

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