从图像中删除白色背景并使其透明 [英] Remove white background from an image and make it transparent

问题描述

我们正尝试在Mathematica中执行以下操作：

  img2 =导入@http://i.stack.imgur.com/k7E1F.png; 
（*关键点：放大图像以平滑边缘*）
 img = ImageResize [img2,4 ImageDimensions [img2]]; 
 mask = ChanVeseBinarize [img，TargetColor  - > {1.，1.，1。}，LengthPenalty - > 10]; 
 mask1 =模糊[侵蚀[ColorNegate [mask]，8]，10]; 
 f [col_]：= Rasterize [SetAlphaChannel [img，mask1]，背景 - > col，
 ImageSize  - > ImageDimensions @ img2] 
 GraphicsGrid [{{f @ Red，f @ Blue，f @ Green}}] 
  

点击放大

编辑2

只是为了了解图像中 halo 的范围和背景缺陷：

  img =导入@http://i.stack.imgur.com/k7E1F.png; 
加入[{img}，MapThread [Binarize，{ColorSeparate [img，HSB]，{。01，.01，.99}}]] 
  

  ColorNegate @ ImageAdd [EntropyFilter [img，1] // ImageAdjust，ColorNegate @ img] 
  

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 lousy (like having a halo around the image).

Here's what we've tried so far:

unground0[img_] := With[{mask = ChanVeseBinarize[img, TargetColor->{1.,1.,1.}]},
  Rasterize[SetAlphaChannel[img, ImageApply[1-#&, mask]], Background->None]]]

Here's an example of what that does.

Original image:

Image with the white background replaced with no background (or, for demonstration purposes here, a pink background):

Any ideas for getting rid of that halo? Tweaking things like LevelPenalty, I can only get the halo to go away at the expense of losing some of the image.

EDIT: So I can compare solutions for the bounty, please structure your solution like above, namely a self-contained function named unground-something that takes an image and returns an image with transparent background. Thanks so much, everyone!

解决方案

Perhaps, depending on the edge quality you need:

img = Import@"http://i.stack.imgur.com/k7E1F.png";
mask = ChanVeseBinarize[img, TargetColor -> {1., 1., 1.}, "LengthPenalty" -> 10]
mask1 = Blur[Erosion[ColorNegate[mask], 2], 5]
Rasterize[SetAlphaChannel[img, mask1], Background -> None]

Edit

Stealing a bit from @Szabolcs

img2 = Import@"http://i.stack.imgur.com/k7E1F.png";
(*key point:scale up image to smooth the edges*)
img = ImageResize[img2, 4 ImageDimensions[img2]];
mask = ChanVeseBinarize[img, TargetColor -> {1., 1., 1.}, "LengthPenalty" -> 10];
mask1 = Blur[Erosion[ColorNegate[mask], 8], 10];
f[col_] := Rasterize[SetAlphaChannel[img, mask1], Background -> col, 
                     ImageSize -> ImageDimensions@img2]
GraphicsGrid[{{f@Red, f@Blue, f@Green}}]

Click to enlarge

Edit 2

Just to get an idea of the extent of the halo and background imperfections in the image:

img = Import@"http://i.stack.imgur.com/k7E1F.png";
Join[{img}, MapThread[Binarize, {ColorSeparate[img, "HSB"], {.01, .01, .99}}]]

ColorNegate@ImageAdd[EntropyFilter[img, 1] // ImageAdjust, ColorNegate@img]

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