Averaging pixels (by downsizing image?) - solved

[redfordxx]

Originally posted by Didée
BTW, in case you want to get the average out of 8*8 blocks, the simplest way is to use Tom's DCTFilter() with
DCFilter(1,0,0,0,0,0,0,0)

And for U,V colors it makes only 4x4 pixel average (as there is half resolution)?

IDEA: how about for 2x2 average(separately for each color - e.g. Y)?

clip
FitY2U
UtoY

or it has same problem as just resize?

[redfordxx]

Originally posted by Didée
use Tom's DCTFilter() with
DCFilter(1,0,0,0,0,0,0,0)

Can you write the formula which is used here?
Can't remember what is (I)DC Transformation...

[redfordxx]

Originally posted by Didée
DCFilter(1,0,0,0,0,0,0,0)

Well, almost works...

almost means that some blocks look like:

22222222
22222222
22222222
11111111
11111111
22222222
22222222
22222222

1 or 2 represent different colors, 1 always little darker than 2.

[Didée]

Aaaah ... yes, of course. DCTFilter(1,0,...) keeps the topmost line and leftmost row /*slaps forehead*/.

DCTFilterD(14) should do the job.

[Si]

So, if using YV12 colourspace then each 4 pixel block shares the same U and V data -yes?

So all thats needed is a 2x2 block averager of the Y plane - yes?

regards
Simon

[redfordxx]

Originally posted by Didée
Aaaah ... yes, of course. DCTFilter(1,0,...) keeps the topmost line and leftmost row /*slaps forehead*/.
DCTFilterD(14) should do the job.

Does not. Same result as that before --- 8x8 blocks with stripe in the middle as I described.
But, what is interesting:
Consequently I was experimenting with idct algo's using following script:

LoadPlugin("C:\PROGRA~1\MULTIM~1\GORDIA~1\AviSynthPlugins\MaskTools.dll")
LoadPlugin("C:\PROGRA~1\MULTIM~1\GORDIA~1\AviSynthPlugins\dgdecode121.dll")

r=mpeg2source("D:\record\rip\lotr tt\1\tt1new.d2v", CPU=0, iDCT=4) # iDCT=4 is "Reference", right?!
r=r.trim(0,5000).crop(4,76,712,424)
d1=mpeg2source("D:\record\rip\lotr tt\1\tt1new.d2v", CPU=0, iDCT=1)
d1=d1.trim(0,5000).crop(4,76,712,424)
d2=mpeg2source("D:\record\rip\lotr tt\1\tt1new.d2v", CPU=0, iDCT=2)
d2=d2.trim(0,5000).crop(4,76,712,424)
d3=mpeg2source("D:\record\rip\lotr tt\1\tt1new.d2v", CPU=0, iDCT=3)
d3=d3.trim(0,5000).crop(4,76,712,424)
d7=mpeg2source("D:\record\rip\lotr tt\1\tt1new.d2v", CPU=0, iDCT=7)
d7=d7.trim(0,5000).crop(4,76,712,424)
s1=YV12Subtract(r,d1,Y=3,U=3,V=3)
s2=YV12Subtract(r,d2,Y=3,U=3,V=3)
s3=YV12Subtract(r,d3,Y=3,U=3,V=3)
s7=YV12Subtract(r,d7,Y=3,U=3,V=3)
StackHorizontal(Stackvertical(s1,s3),Stackvertical(s2,s7)).ColorYUV(cont_y=2048,cont_u=2048,cont_v=2048)

The number 1 and 2 differed from 4=reference mostly in the shape I described. On the other hand, when 3 or 7 differed, it was always nice full blocks.

BTW: Although 4=reference, I tend to like 3 more...

[redfordxx]

Originally posted by Si
So, if using YV12 colourspace then each 4 pixel block shares the same U and V data -yes?

So all thats needed is a 2x2 block averager of the Y plane - yes?

Well I don't understand, whether this is inteded to be question or answer...

[Si]

Its a question

I think what you want can be simply acheived by a simple average of the 4 bytes that make up the [EDIT] 2x2 [/EDIT] pixel block of a Y plane in a YV12 image.

But I didn't want to code it up if it wasn't that easy.

I'm not called Simple Si for nothing

regards
Simon

[redfordxx]

Originally posted by Si
I think what you want can be simply acheived by a simple average of the 4 bytes that make up the 4x4 pixel block of a Y plane in a YV12 image.

Well, whatever plane you are speaking about...

... for this "simple average" I got many answers --- all wrong but the one by Didée: DEdgeMask

[Si]

I finally knocked up a simple filter (BlockAverage) to see if this does what you originally expecting/wanted.



regards
Simon

[redfordxx]

Originally posted by Si
I finally knocked up a simple filter

Well, I havent understood that you're gonna make a filter. Thanks and sorry for making you have effort... because I am already done with the method from Didée and I am averaging all planes 8x8 blocks.