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2D multicolour gradient, how?

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  #1  
Old 12-22-2011, 08:12 AM
drouber drouber is offline
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2D multicolour gradient, how?

Can someone tell me the best method to obtain a 2D colour gradient image from sampling an image at different locations. To clarify things, please take a look here.
I obtained the right image bij combining several radial colour gradient images.
Thanks for all suggestions.
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Old 12-22-2011, 08:46 AM
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Tony W Tony W is online now
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Re: 2D multicolour gradient, how?

One way could be to use radial gradient for your starting background image then add linear gradient starting from the centre working out with the colours you require.

Hope the attached is self explanatory and of help - I did not try and match colours of original or fine tune the effect
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File Type: jpg Grad.JPG (43.3 KB, 27 views)
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Old 12-22-2011, 09:16 AM
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John Wheeler John Wheeler is offline
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Re: 2D multicolour gradient, how?

Hmmm, Tie Dye
Nice Tony

Hi drouber

The end result and control capability is not too clear to me. It might help if you described the project that you are trying to do. Without that here are some random ideas creating 2D gradients.

This first is using a Spectrum gradient in two layers. The first is a radial gradient from center to outside corner, with the second Layer being an Angle gradient from middle to top and then setting the top Layer to Color Blend (Color from Angle gradient and Luminosity from lower radial gradient). You can create custom gradients to create whatever you want:

Radial-Luminosity-Angle-Color.jpg

If you want a more uniform look, this second example is almost identical except I converted the Radial Spectrum gradient to B&W Luminosity and changed to top Angle Gradient Layer to a multiply blend. I have no clue if this is of interest so did not provide tons of details. Let us know a little more of what you are targeting and I am sure forum members can supply more targeted suggestions:

Radial-Luminosity-Multiply-Angle-Color.jpg
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Old 12-22-2011, 10:58 AM
drouber drouber is offline
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Re: 2D multicolour gradient, how?

It looks I need to explain a bit more in detail what I'm looking for.
I think this image explains it better.
The yellow flower to the left has already a soft background but with an interpolated, 2D gradient the flower can be better isolated from its background. An obvious solution is to blur the original and masking out the central object. This will not produce good results because the yellow of the flower will also blur and merge with the green background. By sampling colours around the flower and producing a soft 2D gradient, a useful background can be obtained and masking becomes easy.
I hope this makes clarifies things a bit.
Thanks for all the help and suggestions.

Last edited by drouber; 12-22-2011 at 11:09 AM.
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Old 12-22-2011, 02:23 PM
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Re: 2D multicolour gradient, how?

I think I may have missed the plot here but from the sounds of it all you want to do is mask the flower so that you can apply effects to the background.

Quote:
An obvious solution is to blur the original and masking out the central object. This will not produce good results because the yellow of the flower will also blur and merge with the green background.
I do not understand this, why would the mask also blur the yellow flower and merge with the green background?

Quote:
By sampling colours around the flower and producing a soft 2D gradient, a useful background can be obtained and masking becomes easy.
You should be able to make a satisfactory mask without going to the trouble of producing coloured gradients.

My example
Select Red Channel, make a copy apply curves to adjust contrast to produce a B&W image. A little painting in Overlay mode with white and black should give you a fairly quick mask.

If you apply the left mask to your blur layer you will protect the flower and affect the background (white) only. If you apply the mask on the right you will hide the effect on the background but show on the flower - my example needs mask refining but hopefully should give you the idea
Attached Images
File Type: jpg MaskFlower.jpg (45.8 KB, 14 views)
File Type: jpg MaskFlowerTest.jpg (136.0 KB, 16 views)

Last edited by Tony W; 12-22-2011 at 02:38 PM. Reason: Added image
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Old 12-25-2011, 07:10 AM
drouber drouber is offline
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Re: 2D multicolour gradient, how?

Thanks for all the suggestions and for taking time to help me out.

I'm looking for a quick, universal technique to blur the background of an image without touching some objects (regardless of any color). The right image of the flower gives an idea of what I'm looking for. When you blur the original flower image, the yellow color of the flower merges with the graan colors of the background. By decreasing the size of the blurred image, this smaller image can be used for masking the flower. In this way I obtained the image to the right.

In case of the flower it's easy to get a good mask because of the color difference of the flower (yellow vs green) but what if the flower has the same green color as the background?
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Old 12-25-2011, 11:00 AM
mshi mshi is offline
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Re: 2D multicolour gradient, how?

When other selection tools fail to yield the result that you're trying to get, you can always use Pen tool, which gives you precise control.
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Old 12-25-2011, 07:12 PM
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John Wheeler John Wheeler is offline
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Re: 2D multicolour gradient, how?

Hi Drouber

Ahhh, now I know what you want.

Here are a couple techniques that I have used to achieve what you want (I think).

The first is quick and easy yet not quite as good as the second. And that is to use the box blur instead of something like Gaussian blur. It does not reach under the selection as much so the flower would not be incorporated into the blurred background as much (yet still a little)

The second technique is more involved yet a lot more universal. I will do this on an image from Stock Exchange at http://www.sxc.hu/photo/1373004

1) Duplicate your image (so original is preserved if needed) to a second Layer and make a selection around the object that you don't want blurred. Also, turn off visibility of the first Layers visibility (the original image):
Selection-around-flower.jpg.

2) Save the Selection (Select > Save Selection) and then cut the selection to a third Layer (e.g. Cmd + J for Mac or Ctrl+J for PC). Turn off the visibility of this third Layer which is the Flower in isolation.

3) Go back to 2nd Layer and Load back up the Flower Selection (Select > Load Selection). Use Delete key (Backspace Key for PC) and now you should see transparency where you had selected the flower:
Cute-out-flower.jpg

4) Use Select> Modify > Expand and increase the selection by a few pixels (3 to 10 pixels)

5) Use Edit > Fill > Content Aware Fill. This will fill the transparency with a proxy background similar to:
CAF-back-of-flower.jpg

6) Now blur this Layer. I turn it into a Smart Object first so I can change the blur very easily if I don't like the initial result (I used an extreme amount of blur to demonstrate how the flower is not involved:
Background-Blurred.jpg

7) Turn on visibility of both the original image (eliminates any stray transparency) and also the cut out flower:
Flower-on-blurred-background.jpg

There are other additional steps to adjust edges of foreground to background yet this should get you started.
Hope this helps


ADDED EDIT: One of the issues in any selection process is how much feathering the edge selection has. This can be controlled in many selection tools directly yet not with the Quick Select Tool. It is often easier to see the feathering by turning the selection into a Layer Mask and then directly observing the Layer Mask Opt/Alt Click the Layer Mask Thumbnail. This can be cleaned up when needed with the Refine Edge/Mask Tool. Here is a link to a thread that talks about the feathering of the Quick Select Tool: Thread about feathering with the Quick Select Tool

Last edited by John Wheeler; 12-25-2011 at 09:13 PM.
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  #9  
Old 12-27-2011, 09:08 AM
drouber drouber is offline
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Re: 2D multicolour gradient, how?

@John Wheeler:
Big thanks, this is exactky what I'm looking for. Sorry for my poor explanation in the beginning.
Regards.
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