How to remove constant background from an image?

I'm not sure how to remove the paper background from this logo with v9.

enter image description here

This is really not the same as this question, but I think similar methods apply.

Answer

Not as classy as @belisarius', but:

i1 = Import@"http://i.stack.imgur.com/LKZfw.png"

ColorReplace[i1, RGBColor@PixelValue[i1, {2, 2}], .02]

logo

Edit:

Perhaps it would be better would be to use Vitaliy's method, illustrated in this excellent answer. In this version, the image has a white background, not transparent (hence the difference in color, I suppose):

data = ImageData[i1];
Image[data /. {x_, y_, z_} /; 
    EuclideanDistance[{x, y, z}, data[[2, 2]]] < .3 -> {1, 1, 1}]

logo2

The value of .3 is taken from looking at a ListPlot of the EuclideanDistance values.

Comments

front end - keyboard shortcut to invoke Insert new matrix

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How to thread a list

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