How to Implement the High Pass Filter of Image Processing?
How To Implement The High Pass Filter Of Image Processing?¶
Introduction
If we want to find the high frequency part in the image. We can use the high pass filter. There are a 3 by 3 matrix matching the image. We do the amount of the pixels of the 3 by 3 matrix. The result is the center pixel value of the 3 by 3 matrix. We will rewrite the result in the image.
Equipment
Operation System: Microsoft Windows 7 (64 bit)
Development Utility: Microsoft Visual Studio 2010
Usage
// The high pass filter of 3 by 3 matrix.
double adobHP[3][3] = { {-(0.111), -(0.111), -(0.111) },
{-(0.111), (0.888), -(0.111) },
{-(0.111), -(0.111), -(0.111) } };
// The height ot the image
for ( int iY = 1; iY < imageA->DibInfo->bmiHeader.biHeight - 1; iY++ )
{
// The width of the image
for ( int iX = 1; iX < imageA->DibInfo->bmiHeader.biWidth - 1; iX++ )
{
// A variable
dobFilterResult = 0;
// The height of 3 by 3 matrix
for ( intFWY = -1; intFWY <= 1; intFWY++ )
{
// The height of 3 by 3 matrix
for ( intFWX = -1; intFWX <= 1; intFWX++ )
{
// The index of the image with 3 by 3 matrix. The bit depth is three.
// That is use 24 bits depth of bitmap format.
lIDXA = ( (iX+intFWX) * 3 ) + ( (iY+intFWY) * imageA->DibInfo->bmiHeader.biWidth * 3 );
// Get the pixel of the blue channel.
byteRGB_BA = imageA->DibArry[lIDXA+0];
// Get the pixel of the green channel.
byteRGB_GA = imageA->DibArry[lIDXA+1];
// Get the pixel of the red channel.
byteRGB_RA = imageA->DibArry[lIDXA+2];
// Transform RGB color space to gray scale.
dobYUV_YA = (0.299 * byteRGB_RA + 0.587 * byteRGB_GA + 0.114 * byteRGB_BA);
// The amount of the pixels.
dobFilterResult += ( adobHP[intFWX+1][intFWY+1] * dobYUV_YA );
} // The closing "The height of the 3 by 3 matrix".
} // The closing "The width of the 3 by 3 matrix".
// Using absolute value
dobFilterResult = abs(dobFilterResult);
// The index of the image.
lIDXB = ( iX * 3 ) + ( iY * imageB->DibInfo->bmiHeader.biWidth * 3 );
// Set the pixel of the blue channel.
imageB->DibArry[lIDXB+0] = dobFilterResult;
// Set the pixel of the green channel.
imageB->DibArry[lIDXB+1] = dobFilterResult;
// Set the pixel of the red channel.
imageB->DibArry[lIDXB+2] = dobFilterResult;
} // The closing "The width of the image".
} // The closing "The height of the image".
You can download the source code and binary code.
https://drive.google.com/file/d/0BzHb_OyLyVZlNlNGd0t0UGJvRHM/view?usp=sharing
Exception
There is a notice, if your bit depth of bitmap file are not 24 bits, you should change your bitmap files to adapt this program, or you could rewrite this source code to fit your bitmap format.
You have to install Microsoft SDK v7.1, because I include windowscodes.lib.
#pragma comment(lib, "windowscodecs.lib")
Reference
[1] Gary Bradski and Adrian Kaehler, “Learning OpenCV: Computer Vision with the OpenCV Library,” O’REILLY, September 2008, ISBN:978-0-596-51613-0
Acknowledge
Thank you (Microsoft Visual Studio 2010, Lenna Sjööblom) very much for this great development utility and beautiful photo.
