2D convolution in python

Question

I am taking a basic CS class and in it we have a project where we have to write a code for 2D convolution in python. I have placed the code I have written below:

def Convolve2D(image1, K, image2):
    #iterate over all rows (ignore 1-pixel borders) 
    for v in range(1, image2.getHeight()-1):
        graphics.update() # this updates the output for each row
        # for every row, iterate over all columns (again ignore 1-pixel borders)
        for u in range(1, image2.getWidth()-1):
            # for every pixel, iterate over region of overlap between
            #   input image and 3x3 kernel centered at current pixel
            for i in range (0, 3):
                for j in range (0, 3):                                                                                            
                    # compute output image pixel
                   image2.setPixel(u,v,graphics.color_rgb((image2.getPixel(u,v)[0] + image1.getPixel(u-1+i,v-1+j)[0]*K[i][j]),
                                    (image2.getPixel(u,v)[1] + image1.getPixel(u-1+i,v-1+j)[1]*K[i][j]), (image2.getPixel(u,v)[2]+image1.getPixel(u-1+i,v-1+j)[2]*K[i][j])))

for the last step I have to clamp and set the output image. By clamp I am being asked to use a clamp function that was previously defined as:

def Clamp(pix):
    pix = abs(pix)
    if pix > 255:
        pix = 255
    return pix

but I can't get this last step to work. Any advice would be appreciated.

Maybe I missed it. I don't see where you're calling Clamp(). Are you getting any errors? If so, please post the full traceback. Thank you. — mechanical_meat
– mechanical_meat, Commented Mar 25, 2012 at 0:19
So far I have tried pix=image2.getPixel(u,v) and then Clamp(image2.setPixel(u,v,rbg_color(pix[0],pix[1],pix[2])) since that was how we were shown to set individual pixels for a function. However, I get the error bad operand type for abs():string and I have also gotten the same error but with list at the end — Kristen
– Kristen, Commented Mar 25, 2012 at 0:24
Then you must be passing Clamp a string, when it needs a number. — prelic
– prelic, Commented Mar 25, 2012 at 0:27

Ramchandra Apte · Accepted Answer · 2012-08-02 15:30:45Z

1

As prelic said, then you are passing Clamp a string, when it needs a number.

answered Aug 2, 2012 at 15:30

Ramchandra Apte

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