#66514 - pure_ev1l - Wed Jan 11, 2006 2:37 pm
I am a fairly good programmer which has had a large increase in spare time resently and have just ordered a gba cart. put them all together and I have developed a desire to fill in the blanks of POGO shell.
a good jpeg viewer is needed.... fould one that can re-encode it so its viewable, but thats s*** as the point to jpeg is size.
basicly, all I have found is alot of ppl saying its not possible, which I think is bull after looking into it myself... but I need alittle help...
A) how do you code into plugins? I bet its very simple but I just dont know the basics to the gba as I have only started learning like 4-5 days ago.
B) I have researched the jpeg format heavily (last nite) and I need a few bits of info:
best source I found (and one of the only ones) was http://www.answers.com/topic/jpeg
and to decode it says I need to do the following steps to seperate 8x8 pixel squares tell me if I'm wrong and help explain the bits I dont get if possible:
1) Entropy decoding using Huffman method:
what format is the data saved? byte by byte? after looking at another explanation it seems its in varying sized words with a stop code on end when the rest of the data is not needed so that it is variable length, is this right?
2)adding the difference of the DC coefficient back in
where is this DC coefficent saved in the file, there would need to be one for each 8x8 pixel block, so start / end I guess?
3)multiplying it by the quantization matrix
this bit got me lost. as the explanation of this bit was sparse, what exactly is quatization and where can you retreive those numbers in the jpg?
4) adding 128 to eash element
peice of piss.
5) do this to each channel (brightness, blue, red)
ok, this seems easy to understand, my only question is that it does different compession leves on different channels, any idea where this comes into play? think its the quantization part, not sure.
6)convert back to rgb (or bgr...lol...stupid gba's)
I'm not a total idiot, this shud pose no problem
ok. before you go off on one about how there isn't enough ram...blah blah blah... leave that to me, I think I can cope ;-)... going to use a index to store pointers to locations in jpeg eg line ends or what not, so the gba doesn't need to process whole jpg at once when scrolling or zooming. you may be able to visibly see it decoding, but there is obviously going to be some problem.
ANY input in appreciated as I will release the plugin when it works
a good jpeg viewer is needed.... fould one that can re-encode it so its viewable, but thats s*** as the point to jpeg is size.
basicly, all I have found is alot of ppl saying its not possible, which I think is bull after looking into it myself... but I need alittle help...
A) how do you code into plugins? I bet its very simple but I just dont know the basics to the gba as I have only started learning like 4-5 days ago.
B) I have researched the jpeg format heavily (last nite) and I need a few bits of info:
best source I found (and one of the only ones) was http://www.answers.com/topic/jpeg
and to decode it says I need to do the following steps to seperate 8x8 pixel squares tell me if I'm wrong and help explain the bits I dont get if possible:
1) Entropy decoding using Huffman method:
what format is the data saved? byte by byte? after looking at another explanation it seems its in varying sized words with a stop code on end when the rest of the data is not needed so that it is variable length, is this right?
2)adding the difference of the DC coefficient back in
where is this DC coefficent saved in the file, there would need to be one for each 8x8 pixel block, so start / end I guess?
3)multiplying it by the quantization matrix
this bit got me lost. as the explanation of this bit was sparse, what exactly is quatization and where can you retreive those numbers in the jpg?
4) adding 128 to eash element
peice of piss.
5) do this to each channel (brightness, blue, red)
ok, this seems easy to understand, my only question is that it does different compession leves on different channels, any idea where this comes into play? think its the quantization part, not sure.
6)convert back to rgb (or bgr...lol...stupid gba's)
I'm not a total idiot, this shud pose no problem
ok. before you go off on one about how there isn't enough ram...blah blah blah... leave that to me, I think I can cope ;-)... going to use a index to store pointers to locations in jpeg eg line ends or what not, so the gba doesn't need to process whole jpg at once when scrolling or zooming. you may be able to visibly see it decoding, but there is obviously going to be some problem.
ANY input in appreciated as I will release the plugin when it works