Posts Tagged transparent
Make image backgrounds transparent with tolerance
In one of the projects I am working on at the moment, I needed to convert the background colour of an image to be transparent so the image looks better on a non-white background.
Looking on the Web, I found the following article from Dustin Marx:
Making White Image Backgrounds Transparent with Java 2D/Groovy
If the link is broken, please download his code from the following link: ImageTransparency.java
The method which makes the background colour transparent is called makeColorTransparent. This method works pretty well, except in some cases as shown in the example below:
|
|
| Original image |
Converted image using Dustin’s method |
This is actually quite normal. Indeed, his code is converting a specific colour (#FFFFFF in our case) to be transparent. But what if the background is not homogeneous?
This is the reason why I had to modify his method to add a new parameter called tolerance:
01 | private Image makeColorTransparent(final BufferedImage im, final Color color, int tolerance) { |
02 | int temp = 0; |
03 | if (tolerance < 0 || tolerance > 100) { |
04 | System.err.println("The tolerance is a percentage, so the value has to be between 0 and 100."); |
05 | temp = 0; |
06 | } else { |
07 | temp = tolerance * (0xFF000000 | 0xFF000000) / 100; |
08 | } |
09 | final int toleranceRGB = Math.abs(temp); |
10 | |
11 | final ImageFilter filter = new RGBImageFilter() { |
12 | // The color we are looking for (white)... Alpha bits are set to opaque |
13 | public int markerRGBFrom = (color.getRGB() | 0xFF000000) - toleranceRGB; |
14 | public int markerRGBTo = (color.getRGB() | 0xFF000000) + toleranceRGB; |
15 |
16 | public final int filterRGB(final int x, final int y, final int rgb) { |
17 | if ((rgb | 0xFF000000) >= markerRGBFrom && (rgb | 0xFF000000) <= markerRGBTo) { |
18 | // Mark the alpha bits as zero - transparent |
19 | return 0x00FFFFFF & rgb; |
20 | } else { |
21 | // Nothing to do |
22 | return rgb; |
23 | } |
24 | } |
25 | }; |
26 |
27 | final ImageProducer ip = new FilteredImageSource(im.getSource(), filter); |
28 | return Toolkit.getDefaultToolkit().createImage(ip); |
29 | } |
Such as Photoshop, the tolerance is a percentage value between 0 and 100. The higher the tolerance is, the bigger the range of colours will be.
Let’s take our previous example and apply a 50% tolerance:
That looks much better, isn’t it? 
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