Remove White Background from an Image and Make It Transparent

Question

We\'re trying to do the following in Mathematica - RMagick remove white background from image and make it transparent.

But with actual photos it ends up looking lous

Answer 1

Here's a try at implementing Mark Ransom's approach, with some help from belisarius's mask generation:

Locate the boundary of the object:

img1 = SetAlphaChannel[img, 1];
erosionamount=2;
mb = ColorNegate@ChanVeseBinarize[img, TargetColor -> {1., 1., 1}, 
      "LengthPenalty" -> 10];
edge = ImageSubtract[Dilation[mb, 2], Erosion[mb, erosionamount]];

ImageApply[{1, 0, 0} &, img, Masking ->edge]

Set the alpha values:

edgealpha = ImageMultiply[ImageFilter[(1 - Mean[Flatten[#]]^5) &, 
   ColorConvert[img, "GrayScale"], 2, Masking -> edge], edge];
imagealpha = ImageAdd[edgealpha, Erosion[mb, erosionamount]];
img2 = SetAlphaChannel[img, imagealpha];

Reverse color blend:

img3 = ImageApply[Module[{c, \[Alpha], bc, fc},
   bc = {1, 1, 1};
   c = {#[[1]], #[[2]], #[[3]]};
   \[Alpha] = #[[4]];
   If[\[Alpha] > 0, Flatten[{(c - bc (1 - \[Alpha]))/\[Alpha], \[Alpha]}], {0., 0., 
   0., 0}]] &, img2];

Show[img3, Background -> Pink]

Notice how some of the edges have white fuzz? Compare that with the red outline in the first image. We need a better edge detector. Increasing the erosion amount helps with the fuzz, but then other sides become too transparent, so there is a tradeoff on the width of the edge mask. It's pretty good, though, considering there is no blur operation, per se.

It would be instructive to run the algorithm on a variety of images to test its robustness, to see how automatic it is.