Subject:
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Re: How to color a source image for building a mosaic?
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Newsgroups:
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lugnet.build.mosaic
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Date:
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Fri, 18 Jan 2008 00:15:52 GMT
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Viewed:
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15925 times
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In lugnet.build.mosaic, Maarten Steurbaut wrote:
> In lugnet.build.mosaic, Tony Locke wrote:
> > I am planning a mosaic and have parts in 6 colors (an equal number of 1x1
> > squares in each color). I'm trying to convert my source image (using Photoshop)
> > into my 6 color in such a way that the source image contains an equal number of
> > pixels of each of the 6 colors. I can then use this image as a map for building.
> >
> > Is there a way to do this in Photoshop, or using any other software?
> >
> > Many thanks for any advice,
> > Tony
>
> Tony,
>
> I don't think there's any kind of software that can do just that for you; you'll
> need some programming skills to do it yourself:
>
> Just suppose you want to make a grayscale mosaic --> 5 colors --> 20% of each
> color.
> Calculate the "degree of darkness" of every pixel in your original image (I use
> RGB color-values): squareroot(square(R)+square(G)+square(B)). This is the
> distance in space from the origin (0,0,0) which is black to the current pixel.
> Sort all the pixels in an array from darkest to lightest.
> The 20% darkest pixels should be turned into black,..., the 20% lightest pixels
> turn into white.
> I'm sure it'll work for grayscale images. The only problem that might occur is
> that there are too many pixels in the original image that have exactly the same
> RGB color-value. In that case you may have to add some sort of random function.
>
> A good example of this "degree of darkness" can be found on Eric Harshbarger's
> website: his modulex mosaic of Calista Flockhart. I also used it for the
> ministeck mosaic of my kids.
>
> A similar procedure can be followed to make a mosaic with "real" colors, if you
> order them from darkest to lightest. That's how I made my "nightclub" ministeck
> mosaic (I did exactly the opposite: I turned a grayscale image into a colored
> one).
>
> You have to calculate the distance in RGB-space from every pixel to each of the
> six colors you want to use, to divide all the pixels into 6 equal groups: 16.67%
> pixels closest to color 1,..., 16.67% pixels closest to color 6. Unfortunately
> these groups will overlap each other in most cases.
> You may decide to convert 16.67% closest to color 1 first, of all the remaining
> pixels then convert 16.67% closest to color 2,... but I can't predict what the
> result will look like (can't you get rid of the idea of 6 equal amounts?...).
>
> Hope this helps to get you started,
> Maarten
Hi Maarten,
Many thanks for your suggestion. Unfortunately, I'm no programmer, but I think
that it would be possible to perform the calculations you describe in a
spreadsheet, if provided with the RGB values for each pixel in the image. I do
not know however how to extract this information from an image (except manually,
pixel by pixel).
I'm sure there must be a way of converting an image file into a text file,
extracting the relevant pixel data, performing the calculations, then pasting
the amended pixel data back into the text file and converting back to an image
file. I'll search around online to try and find a way of doing this... if anyone
has come across a way of doing this, I'd be most grateful for any suggestions.
Cheers,
Tony
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