Processing Only One Channel Of An Image

[user_deleted]

Hey, I was wondering if there was any way to process only one channel of an image instead of 3 or 4. Say I want to rotate a grayscale image. Shake rotates all four channels even though the first three will have the same result. I don't want to just reorder the channels for null's, I don't want them processed at all. Any ideas? Thanks.

[user_deleted]

hi iamquand,

just try to use the reorder nodes.
u can separate each channel then, and do everything u like with it.

greetz

telepilot

[joojaa]

one can prebtach the files to 1 channel files.... se the manual on this.

[user_deleted]

question is: why do you want to do it? Shake is clever enough to know which channels it need for the fileouts. So it only renders the channels it really needs. If you have some nodes and feed the final output to the matte input of another node, shake will only render the alpha channel of the whole branch, because it only needs the alpha.

So is their really a need for limiting shake manually?

[user_deleted]

I think you guys are misunderstanding. This isn't for a FileOut node, this is to save time during the processing of an effect. When doing a reorder, Shake will still process all four channels even if they are blank. It still says "this channel is blank and has a color of black" So it evaluates the pixels which quadrupuals the processing time on specific effects.

I'll have to look into prebatching etc.

[user_deleted]

no, I think you are misunderstanding: which processing time do you mean, the time shake needs inside of the GUI or the processing while Shake renders a script?

If you mean the time shake needs to render a setup, then have a look at my previous comment. When Shake renders, it examines the script from bottom to top and Shake knows which channels it needs to render and which it can ignore.

And in addition: I would guess that most of the nodes has algorithms where it wouldn't make any significant change in rendertime if it would render 1 channel instead of 3 or 4.

Just try it: add a reorder node to your script with "rrrn" as value. This converts your image to a black and white only image, which has only one channel. Then measure the time it takes to render the same nodes with and without this reorder node.

[user_deleted]

QUOTE(shakebox @ 12/06/05, 10:50 AM)
Just try it: add a reorder node to your script with "rrrn" as value. This converts your image to a black and white only image, which has only one channel. Then measure the time it takes to render the same nodes with and without this reorder node.
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I'm going to post this shake example of what you're talking about. There are 3 outputs, one has a reorder(rrrr) and then a randomize, one has reorder(rrrn) and then randomize, and one has randomize then reorder(rrrn). All 3 outputs take the same amount of time. Also, if you view the Randomize2 (on the right) it takes the same amount of time that it does to render after the reorder. Render times are the same with flipbook render as well. Randomize2 is full color, so it obviously will operate on all channels. Based on render times, even the gray versions are rendering all channels no matter when the reorder takes place. I was hoping I could do something to make it take 1/3 or 1/4 the time when I only want to operate on gray.

Here is my script:
___________________________________________________

// Input nodes

ColorWheel1 = ColorWheel(720, 486, 1, 0, 1, 1, 1);

// Processing nodes

Randomize2 = Randomize(ColorWheel1, 4, 57, 60, xAmplitude, 5.4,
0);
Reorder1 = Reorder(ColorWheel1, "rnnn");
Reorder3 = Reorder(ColorWheel1, "rrrr");
Randomize1 = Randomize(Reorder1, 4, 57, 60, xAmplitude, 5.4,
0);
Randomize3 = Randomize(Reorder3, 4, 57, 60, xAmplitude, 5.4,
0);
Reorder2 = Reorder(Randomize2, "rrr0");

____________________________________________________________

[user_deleted]

I think we are both right actually. I noticed in the info line when I have the colorwheel linked to a Reorder node of "rrrn" and i scroll over the reorder node it says "BW" in the info line. When I have "rgba" in the reorder node then it says "rgba" in the info line. So shake knows that it's only supposed to opperate on one channel yet it still processes all four. Bizzare.

[joojaa]

its because you ghave reorder "rrrr" rather than "r" or "r000" and because your inside the GUI, if you batch it without gui shake does doe it differently, shake renders faster faster form commandfline because the GUI will need the 3 channels anyway.