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Quasimondo
Quasimondo
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There are a few things that I'd just like to know how they are handled internally - right now I've got two questions:
- When I extract a channel from an image I get a greyscale image - does Filter Forge internally treat this as 3 channels with equal content like Photoshop does or is this somehow optimized?
- When I plug a normal color image into an input that is usually handled by a slider ("offset" or "percentage" for example) - how is the color information of the image converted? Is it luminance, the brightness, the red channel?
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| Posted: June 6, 2006 2:52 pm |
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Kraellin
Kraellin
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all of the extract components extract channels the same way psp does, into grayscale bitmaps. therefore, you cant apply any color/hue/saturation operation to them and change them at all. photoshop does it differently in that you can see the represented colors added back in. psp, and apparently FF dont do that last step.
the content is not equal. the shades of gray of each channel correspond to a color value for that color channel. so, all you can alter when you split the channels in FF is the gray scale values. applying HUE to the grays wont do anything and the same with saturation.
so, the only thing you can change in an extracted channel is the lightness, which will affect the color of that channel.
craig If wishes were horses... there'd be a whole lot of horse crap to clean up!
Craig |
| Posted: June 6, 2006 3:31 pm |
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byRo
an Englishman in Brazil
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Quasimondo wrote:
- When I plug a normal color image into an input that is usually handled by a slider ("offset" or "percentage" for example) - how is the color information of the image converted? Is it luminance, the brightness, the red channel? |
I had thought that the answer was simple - until I did some tests. (see attachment).
I had thought that it would be just the Luminosity (or it's correspondent channel), but now I am just plain confused.
Seems that I'll have to wait until onyXMaster comes along to un-befuddle me.
Rô  _________________________________
My favourite question is "Why?".
My second favourite is "Why not?"
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| Posted: June 6, 2006 8:42 pm |
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Vladimir Golovin
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Quasimondo wrote:
does Filter Forge internally treat this as 3 channels with equal content like Photoshop |
That's correct.
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Quasimondo wrote:
ormal color image into an input that is usually handled by a slider ("offset" or "percentage" for example) - how is the color information of the image converted? |
The default is non-weighted averaged RGB, but you can customize the conversion by simply converting the source image to B/W yourself before feeding it into the slider input.
For example, if you plug a Desaturation component between the source and the grayscale (slider) input, you'll be able to choose from 3 desaturation methods, one of which is weighted average.
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| Posted: June 7, 2006 5:59 am |
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byRo
an Englishman in Brazil
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Vladimir, thanks for un-befuddling me.
As we are talking about "Internal Workings", what mode does FF work in?
Here we have RGB (and unwieghted too!), for colour blending we have HSY.
If it's a "trade secret", I didn't ask. OK?
Rô _________________________________
My favourite question is "Why?".
My second favourite is "Why not?"
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| Posted: June 7, 2006 6:30 am |
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Quasimondo
Quasimondo
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Vladimir - thank you very much for this information!
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| Posted: June 7, 2006 6:44 am |
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Vladimir Golovin
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byRo wrote:
what mode does FF work in? |
If I understand the question correctly, the pipeline uses RGBA with double-precision floating point values for each component. Bitmap-based components (Blur, Motion Blur, Sharpen, High Pass) use single-precision for their caches except when they are plugged into the Height input (they use double in this case).
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byRo wrote:
If it's a "trade secret", I didn't ask. OK? |
It's hard to hide any trade secrets from you guys -- you'll figure them out anyway 
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| Posted: June 7, 2006 7:06 am |
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Vladimir Golovin
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Vladimir Golovin wrote:
Quasimondo wrote: does Filter Forge internally treat this as 3 channels with equal content like Photoshop
That's correct. |
UPDATE: The above quote is incorrect. Filter Forge uses an optimized single-channel grayscale. Sorry for the confusion.
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| Posted: June 7, 2006 8:15 am |
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byRo
an Englishman in Brazil
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Vladimir Golovin wrote:
If I understand the question correctly.... |
Yes you did, thank you. 
So if I understood your answer correctly that means that when you do the math in HSY for the "Color" mode in the Blend component, that is an exception and not the rule. Especially considering that blending colour isn't something that comes "naturally" in RGB.
Rô
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My favourite question is "Why?".
My second favourite is "Why not?"
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| Posted: June 7, 2006 10:37 am |
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Vladimir Golovin
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byRo wrote:
"Color" mode in the Blend component, that is an exception and not the rule |
Correct.
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| Posted: June 7, 2006 11:39 am |
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