Commons:Graphics village pump/February 2012

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How do I volunteer?[edit]

Hi there, I have just joined up and am keen to volunteer my services as a digital designer to assist in amending pictures, (removing red eye etc…) Forgive my ignorance, I have tried to find out how to do this, but unfortunately do not understand the procedure. Can anyone talk me through the steps please of finding the image, downloading it so that I can edit it and then uploading it back to wikimedia once I have amended the issues? I look forward to any help Kind Regards Conor -- 14:37, 10 February 2012‎ User:Conor2000

Sorry I didn't see this before, but this is kind of a Help Desk problem... AnonMoos (talk) 07:09, 20 February 2012 (UTC)

Happy to Help Out on Custom Programs - especially for Pseudocolor[edit]

I might have one rather unique talent that could be contributed: If an image needs something not available in the standard suite of commercial products, I can load it into Mathematica and apply a custom, unique algorithm built especially for the problem at hand. That might take a few days of work per image. So, if any of you see something like that, let me know. If I am not currently active at that time, you can email me at doug@youvan.com . In general, you can see some of my image processing work at http://www.youvan.com . In particular, this application is ready to apply: http://youvan.com/Source_Code_PDF/3.pdf , and it could be used for a rather fancy rescaling of image pseudocolor. I can also do unique grayscale -> pseudocolor lookup schemes customized for a particular problem. I've been working in image processing since the days when memory was $1 / byte, a 50kB drive cost $50,000 in 1987! Doug youvan (talk) 14:47, 9 January 2012 (UTC)

Oh, I have something else that might be useful in a special case. Consider that we usually clip grayscale and color information outside of the 0 - 255 range, "real color". Let's call anything < 0, "anticolor" and anything > 255, "supercolor". Usually, anticolor and supercolor get clipped to black and white, but there are some cases (sequential algorithms) where that information is useful to keep. With algos that would normally clip, the information is lost for a (next) algo that might bring it back into the real color range. I am currently active in that area with my "Tuple Images". I say that, because once you put away code for a few weeks, it is difficult to restart - like not being able to read your own code! So, again, I am willing to help on very special images where unique algos are needed on a per image basis. My efforts are non-commercial and pro bono, as in "retired". Doug youvan (talk) 15:16, 9 January 2012 (UTC)

Removing the flash[edit]

I have recently seen a huge portrait, which is in the public domain and may be uploaded. I took a photo without flash, but it's very dark and blurred. Then I took one with flash, but there's a big ugly light reflection in the portion of the portrait where the flash was pointing. So, I took some other photos from the angles, at 45º instead of watching the portraint in the front. Of course, the angle is not right, and they also have the flash reflection, but somewhere else.

My question: is it possible to use the photos taken from an angle to "fix" the front photo, and replace the area with the flash reflection? Cambalachero (talk) 00:18, 20 February 2012 (UTC)

Possibly, but it would take a lot of work to try to patch things in to look somewhat seamless. You need to use what Adobe Photoshop calls the "skew" or "perspective" tools (might have a different name in another graphics program) to transform the geometry of the relevant area of the side-view photo to match the geometry of the front-view photo. Then there might be brightness and color differences to try to match... AnonMoos (talk) 07:24, 20 February 2012 (UTC)
If you are using GIMP for editing then I highly recommend the Image Registration plugin. It aligns images automatically and does it more accurately than is possible by hand. —Quibik (talk) 10:23, 24 February 2012 (UTC)

Graduated outline on a shape[edit]

Test of application of a graduated outline on a shape.

Could any raw SVG (not Inkscape users) help me with my attempt to apply a graduated outline on a shape, please?

As far as I can tell, SVG supports linear and radial gradients, but not gradients following a path. I tried to simulate this by having overlapping semitransparent strokes of different widths, as in the image on the right. Other than the stepwise appearance of the gradient, which can be remedied with more layers, there are several undesirable artifacts:

  1. Ugly islands appear where strokes from two disconnected parts meet e.g. between Ireland and Wales in the left map
  2. The gradient gets denser where there is more detail e.g. in west Scotland
  3. There are some strange anomalies e.g. white patches emanating southwards from the tip of Cornwall and the Isle of Wight

Would you know any solutions to these issues, or a better method to make such gradients in raw code?

As an aside, I cleared the inward gradient of the left map by overlaying the map filled solid white. Is it possible to create a clip-path which is the negative of the one for the right map, which can be applied to give the appearance of the left map without the solid fill?

Thanks,
cmglee (talk) 11:30, 26 February 2012 (UTC)


The quick-and-dirty solution is to stroke a series of lines along the path, each line having slightly different width and color. This results in a stepped effect, but you can approximate a gradient by using a large number of lines. If you only want a gradient on the outside of the path, then you fill the path after having stroked... AnonMoos (talk) 18:06, 27 February 2012 (UTC)
Oops, I guess that's what you were already doing (sorry I misunderstood). PostScript level 3 has some operators which should allow what you want, but I don't understand the details (which seem to be mathematically complex), nor whether there's a PS-to-SVG conversion path... AnonMoos (talk) 18:13, 27 February 2012 (UTC)
P.S. Some of your problems were probably due to the fact that this method only really allows the thickest line to be partially transparent; other lines must be fully opaque. I uploaded a version of File:Test outline gradient.svg eliminating non-zero opacity; you could fiddle with the colors further (and greatly increase the number of strokes) to achieve something close to the desired result. By the way, in Adobe SVG plugin, the southern coast of western Cornwall shows a kind of "kink" in the contours, but there is no intrusive white zone. Probably the map outline has a strange hidden curve deformity at that point... AnonMoos (talk) 18:35, 27 February 2012 (UTC)
Eliminated the Cornwall anomaly by running the curves through Fontforge... AnonMoos (talk) 00:53, 28 February 2012 (UTC)
Many thanks, AnonMoos; your advice and fixing the anomalies are much appreciated. It's a shame that the outlines must be opaque — that limits the use of such gradients in many cases :( cmglee (talk) 22:44, 4 March 2012 (UTC)

Banding caused by Gaussian blur[edit]

How do I get rid of banding caused by heavy Gaussian blur? I apply RGB noise but this is not always sufficient. I use GIMP, I don't have Photoshop, so if you know how to do this in GIMP that would really be great. Thank you! Gidip (talk) 23:36, 28 February 2012 (UTC)

You may get more answers on a hard-core raster-editing forum (which this isn't). I'm not too sure what Gaussian blur is, but if I want an extra-powerful non-noise-introducing blurring or smoothing function, I use the Photoshop "Median" filter (not sure what the GIMP equivalent is)... AnonMoos (talk) 01:20, 29 February 2012 (UTC)