CODEWITHSUNDEEP
c++image-processinggaussian
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Reputation: 505

How to make Gaussian Blur work properly?

I'm writing a Gaussian Blur filter with 3x3 matrix(kernel) and using QImage as external library. The kernel is calculated as it has to be. After kernel is initialized and calculated I bring the unsigned int Matrix into the program: 

typedef std::vector<std::vector<unsigned int> > uintMatrix; // For copying pixels value

In the main.cpp it's initialized like:

uintMatrix tmpPxMat(image.width(); std::vector<unsigned int> (image.height(), 0));

I use it as a temporary storage for blurred pixels values.

Then, I use my algorithm to blur the image:

// Blur Pixels
for(int x = 0; x < image.width(); x++)
    for(int y = 0; y < image.height(); y++) {
        // To avoid edge cases don't process them, I'll fix it soon
        if(x == 0 || x == image.height()-1 || y == 0 || y == image.width()-1)
            continue;
        // 3x3 Matrix
        tmpPxMat[x][y] += kernel[0][0] * image.pixel(x-1, y-1) +
                          kernel[0][1] * image.pixel(x, y-1) +
                          kernel[0][2] * image.pixel(x+1, y-1);

        tmpPxMat[x][y] += kernel[1][0] * image.pixel(x-1, y) +
                          kernel[1][1] * image.pixel(x, y) +
                          kernel[1][2] * image.pixel(x+1, y);

        tmpPxMat[x][y] += kernel[2][0] * image.pixel(x-1, y+1) +
                          kernel[2][1] * image.pixel(x, y+1) +
                          kernel[2][2] * image.pixel(x+1, y+1);
    }

Then, I copy the result of tmpPxMat[][] to the origin image:

// Copy blurred values to the image
for(int x = 0; x < image.width(); x++)
        for(int y = 0; y < image.height(); y++)
            image.setPixel(x, y, tmpPxMat[x][y]);

And save it:

image.save("/home/john/Pictures/blurred", "PNG", 100);

But at the end I get not the result I was waiting for. Here what I get:

Before / After:

Origin/Blurred

Sorry for the long question description, but I compressed it as much as I could.

Upvotes: 2

Views: 1405

Answers (1)

Adrian McCarthy
Adrian McCarthy

Reputation: 48019

I assume uintMatrix is a two-dimensional array of 32-bit ints, and that you've packed the red, green, and blue channels into that.

If so, that's your problem. You need to blur each channel independently.

Upvotes: 3

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