#31400 - QuantumDoja - Fri Dec 10, 2004 8:18 pm
Hi, How does pcx2gba work, i understand that it takes to pixels and puts them into a hexadecimal value (how??)
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Chris Davis
#31420 - tepples - Fri Dec 10, 2004 10:08 pm
What an image conversion program does, at the highest level: - Decode the image file, based on format specs from wotsit.org
- Reorder the pixels in a GBA format, according to GBATEK
- Write the pixels to a file
Which step do you need explained further?
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#31427 - QuantumDoja - Fri Dec 10, 2004 10:55 pm
Well, you have to hex values of 2 pixels, then what, how do they get converted into one?
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Chris Davis
#31429 - Lupin - Fri Dec 10, 2004 11:01 pm
no need to convert them into one.
Just copy 2 pixels at the same time - will also be faster.
If you really feel like you would need to access 1 pixel at a time:
firstpixel = pixeldata[y*WidthOfImage+(x>>1)] >> 8;
secondpixel = pixeldata[y*WidthOfImage+(x>>1)+1] & 0xFF;
WidthOfImage needs to be the half of the actual width because the array stores 2 pixels in 1 array-element. Don't you read tutorials about GBA programming? www.thepernproject.com is very good and it should give you informations about things like this i think
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#31442 - QuantumDoja - Sat Dec 11, 2004 12:18 am
Hi, Dovoto's program puts tile data like so..
const u16 TileData[] = {
0xFEFE, 0xFEFE,...
Each hex value is 2 pixels, I was wondering how, for instance, if you had two color codes:
#002299 and #ff00ff you combine them to squaeeze them into the 16 bit int. What would the value be?
please help.
Thanks
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Chris Davis
#31453 - tepples - Sat Dec 11, 2004 12:44 am
You can read GBATEK or the CowBite spec to see how to format a 15-bit color. What did you not understand after reading those documents?
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#31454 - Lupin - Sat Dec 11, 2004 12:46 am
oh... well, these color codes are 24 bit color.
In 24/32 bit color mode Red, Green and Blue have 8 bits (each channel = 8 bits/1 byte) so you can have red/green/blue values from 0 to 255
In 16 bit (actually 15 bit) color mode Red, Green and Blue only have 5 bits (5*3 = 15) so you can have red/green/blue values from 0 to 31
Understanding binary/hex system helps a lot for understanding this kind of calculation.
When you convert a 24 bit color to 15 bit color you divide the Red/Green/Blue value by 8 and combine the result into one 16 bit half word - voila you have your 15 bit color!
Some systems may use different order of R/G/B values...
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#31520 - QuantumDoja - Sat Dec 11, 2004 9:21 pm
Ok. what i want to do is from these two hex values make the single value:
We already know what the pixel colors will be, as below
ok:
pixel1: #00ff00
pixel2: #ffff00
Output: 1 hex value.
just need to put them into one. Does it matter im using web hex codes?
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Chris Davis
#31523 - tepples - Sat Dec 11, 2004 9:33 pm
Converted from hex to decimal:
Pixel 1: R=0, G=255, B=0
Pixel 2: R=255, G=255, B=0
The components of a web color range from 0 to 255, while the components of a GBA color range from about 8 to 31. To convert each web color component x to a GBA color component x', do x' = x / 11 + 8.
This gives the GBA colors:
Pixel 1: R=8, G=31, B=8
Pixel 2: R=31, G=31, B=8
Given these, each GBA pixel value is R + 32*G + 1024*B.
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#31527 - Lupin - Sat Dec 11, 2004 9:51 pm
Why do you think they Colors for a GBA pixel reach from 8 to 31? I am quite sure that they reach from 0 to 31 =/
The equalation should just be x' = x / 8
As example take web color component 255 for x this will give us x' = 255/8 = 31,875 (don't round this up)
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#31531 - QuantumDoja - Sat Dec 11, 2004 10:48 pm
So, with that said, in this case, what is the answer?
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Chris Davis
#31532 - Lupin - Sat Dec 11, 2004 11:12 pm
I don't know what you expect as an answer to this... but if you still don't have enough info, here is a simple VB function that takes a normal 24 bit color and converts it to a GBA 15 bit color, i use this function in my converters:
| Code: |
Private Function C24toC15(c As Long) As Integer
Dim cr As Long, cg As Long, cb As Long
cr = ((c And &HFF) \ 8) * 1024
cg = (((c \ &H100) And &HFF) \ 8) * 32
cb = ((c \ &H10000) And &HFF) \ 8
C24toC15 = cr Or cg Or cb
End Function
|
The return type is Integer (16 bit), the input type is Long (32 bit). In C you would do the * and \ with shift operators but VB doesn't support them =/
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#31538 - keldon - Sun Dec 12, 2004 1:11 am
| Lupin wrote: |
Why do you think they Colors for a GBA pixel reach from 8 to 31? I am quite sure that they reach from 0 to 31 =/
The equalation should just be x' = x / 8
As example take web color component 255 for x this will give us x' = 255/8 = 31,875 (don't round this up) |
Because 0-7 are pretty much the same shades of pitch black.