How to blur a portion of an image with JAVA

Question

How to blur a portion of an image, to hide some privates parts like credit card informations.

I try to use ConvolveOp.class like :

float[] matrix = new float[400];
for (int i = 0; i < 400; i++)
    matrix[i] = 1.0f/500.0f;

BufferedImage sourceImage =  (BufferedImage) image; ;
BufferedImage destImage = null ;
BufferedImageOp op = new ConvolveOp( new Kernel(20, 20, matrix), ConvolveOp.EDGE_NO_OP, null );
BufferedImage blurredImage = op.filter(sourceImage, destImage);

it seems to work, except that the image is completely blurred.

I can't really help you, that being said I just wanted to chime in and tell you that your question actually taught me something about Convolving images and blurring, so thanks for that ! :) — Christophe Schutz, Jul 27 '15 at 09:57

score 3 · Answer 1 · edited Jul 30 '15 at 10:40

3

In the case you want to focus on the application and not on the specifics of image processing, you can use an image processing framework like Marvin. Thus, you can do more with less code.

Input image:

Output image:

Source code:

import static marvin.MarvinPluginCollection.*;

public class PortionBlur {
    public PortionBlur(){
        // 1. Load image
        MarvinImage image = MarvinImageIO.loadImage("./res/credit_card.jpg");

        // 2. Create masks for each blurred region
        MarvinImageMask mask1 = new MarvinImageMask(image.getWidth(), image.getHeight(), 38,170,345,24);
        MarvinImageMask mask2 = new MarvinImageMask(image.getWidth(), image.getHeight(), 52,212,65,24);
        MarvinImageMask mask3 = new MarvinImageMask(image.getWidth(), image.getHeight(), 196,212,65,20);
        MarvinImageMask mask4 = new MarvinImageMask(image.getWidth(), image.getHeight(), 38,240,200,20);

        // 3. Process Image with each mask
        GaussianBlur gaussianBlur = new GaussianBlur();
        gaussianBlur.load();
        gaussianBlur.attributes.set("radius",15);

        gaussianBlur.process(image.clone(), image, mask1);
        gaussianBlur.process(image.clone(), image, mask2);
        gaussianBlur.process(image.clone(), image, mask3);
        gaussianBlur.process(image.clone(), image, mask4);

        // 4. Save the final image
        MarvinImageIO.saveImage(image, "./res/credit_card_out.jpg");
    }
    public static void main(String[] args) {
        new PortionBlur();
        System.exit(0);
    }
}

Gaussian blur algorithm source code:

https://github.com/gabrielarchanjo/marvinproject/blob/master/marvinproject/dev/MarvinPlugins/src/org/marvinproject/image/blur/gaussianBlur/GaussianBlur.java

edited Jul 30 '15 at 10:40

Karim Oukara

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answered Jul 29 '15 at 12:34

Gabriel Archanjo

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but what is the gaussianBlur method in this case ? – Karim Oukara Jul 29 '15 at 13:17
gaussianBlur(input_image, output_image, radius, pixels_mask) blurs the image using a Gaussian function. Gaussian Blur on Wikipedia: https://en.wikipedia.org/wiki/Gaussian_blur – Gabriel Archanjo Jul 29 '15 at 13:30
can you give us an example of this method using java ? – Karim Oukara Jul 29 '15 at 13:35
accourding to your recent changes, I edited your answer – Karim Oukara Jul 30 '15 at 09:36
It's not safe to use for real cards, because Gaussian blur can be reversed. – setec Jul 30 '15 at 10:28
You suggest what, for a safe use? – Karim Oukara Jul 30 '15 at 11:22
@GabrielAmbrósioArchanjo is it possible to retrieve an image from a URL ? like `MarvinImageIO.loadImage("URL");` – Karim Oukara Jul 30 '15 at 14:49
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@KarimOukara You can request an image from URL, create a BufferedImage and then create a MarvinImage using the constructor new MarvinImage(BufferedImage). Loading image from URL in Java: http://stackoverflow.com/questions/3986891/how-can-i-read-image-from-url-in-java – Gabriel Archanjo Jul 30 '15 at 15:13

Siguza · Accepted Answer · 2015-07-27T14:50:53.777

1

I don't know whether this can be done by changing the matrix values, but this should definitely be possible by filtering a subimage, since, according to the BufferedImage.getSubimage() documentation:

The returned BufferedImage shares the same data array as the original image.

So the original BufferedImage should change with code like this:

BufferedImage image = /* ... */;
BufferedImage subImage = image.getSubimage(10, 20, 30, 40); // x, y, width, height
new ConvolveOp(new Kernel(20, 20, matrix), ConvolveOp.EDGE_NO_OP, null).filter(subImage, subImage);

I didn't test this though, and I can imagine that filter doesn't work as expected if source and destination are the same, in which case you could use a copy of the subimage, using the solution from this question:

BufferedImage image = /* ... */;
BufferedImage dest = image.getSubimage(10, 20, 30, 40);  // x, y, width, height
ColorModel cm = dest.getColorModel();
BufferedImage src = new BufferedImage(cm, dest.copyData(dest.getRaster().createCompatibleWritableRaster()), cm.isAlphaPremultiplied(), null).getSubimage(0, 0, dest.getWidth(), dest.getHeight());
new ConvolveOp(new Kernel(20, 20, matrix), ConvolveOp.EDGE_NO_OP, null).filter(src, dest);

After that, continue working with image (not subImage, src or dest!)

edited Jul 27 '15 at 14:50

answered Jul 27 '15 at 10:22

Siguza

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This solution cuts the image into two parts. is it possible to merge then ? – Karim Oukara Jul 27 '15 at 11:41
What do you mean "into two parts"? A blurred area and a non-blurred area? Or what exactly happens? Because as I said, I didn't test this. – Siguza Jul 27 '15 at 11:51
Yes the blurred area and a non-blurred area are separated. – Karim Oukara Jul 27 '15 at 11:56
But like... next to each other, or one actually inside the other? – Siguza Jul 27 '15 at 11:57
sorry for the quality of my English. So, the problem is that I do not know how to save the changes on the image. I try to create a new image (with the blur), however it save only a part of the image (blurred area) !!! – Karim Oukara Jul 27 '15 at 12:08
Try saving `image` itself - it should change. – Siguza Jul 27 '15 at 12:11
it does not work like that. We must save the buffredImage. AS BufferedImage blurredImage = op.filter(subImage, null); ImageIO.write(blurredImage, "jpg", new File(".../image.jpg")); – Karim Oukara Jul 27 '15 at 12:18
Dude. You have a `BufferedImage` called `image`. And you have a part of that, also a `BufferedImage` called `subImage`. You are obviously saving `subImage`. I'm telling you to save `image` instead. Because `subImage` and `image` share the same array of pixels, `image` should change as well, when `subImage` is filtered. – Siguza Jul 27 '15 at 12:21

How to blur a portion of an image with JAVA

2 Answers2