MimFFT
This program uses the Fast Fourier Transform to filter an image.
Language: C#
Functions used: MappAlloc, MappFree, MbufAlloc2d, MbufChild2d, MbufClear, MbufCopy, MbufFree, MbufLoad, MbufPut2d, MdispAlloc, MdispControl, MdispFree, MdispInquire, MdispSelect, MgraArc, MimTransform, MsysAlloc, MsysFree
Categories: Overview, General, Industries, Electronics, Applications, Preprocessing, Modules, Buffer, Display, Graphics, Image Processing, What's New, Older
///////////////////////////////////////////////////////////////////////////////
// Aurora Imaging Library
// Filename: MImFFT.cs
//
// Description: This program uses the Fast Fourier Transform to filter an image.
//
// (C) 1992-2026 Zebra Technologies Corp. and/or its affiliates
// All Rights Reserved
///////////////////////////////////////////////////////////////////////////////
using System;
using System.Collections.Generic;
using System.Text;
using Zebra.AuroraImagingLibrary;
namespace MImFFT
{
class Program
{
// Target image specifications.
private const string NOISY_IMAGE = AIL.M_IMAGE_PATH + "noise.mim";
private const int IMAGE_WIDTH = 256;
private const int IMAGE_HEIGHT = 256;
private const int X_NEGATIVE_FREQUENCY_POSITION = 63;
private const int X_POSITIVE_FREQUENCY_POSITION = 191;
private const int Y_FREQUENCY_POSITION = 127;
private const int CIRCLE_WIDTH = 9;
static void Main(string[] args)
{
AIL_ID AilApplication = AIL.M_NULL; // Application identifier.
AIL_ID AilSystem = AIL.M_NULL; // System identifier.
AIL_ID AilDisplay = AIL.M_NULL; // Display identifier.
AIL_ID AilImage = AIL.M_NULL; // Image buffer identifier.
AIL_ID AilOverlayImage = AIL.M_NULL; // Overlay image buffer identifier.
AIL_ID AilSubImage00 = AIL.M_NULL; // Child buffer identifier.
AIL_ID AilSubImage01 = AIL.M_NULL; // Child buffer identifier.
AIL_ID AilSubImage10 = AIL.M_NULL; // Child buffer identifier.
AIL_ID AilSubImage11 = AIL.M_NULL; // Child buffer identifier.
AIL_ID AilTransformReal = AIL.M_NULL; // Real part of the transformed image.
AIL_ID AilTransformIm = AIL.M_NULL; // Imaginary part of the transformed image.
float[] ZeroVal = new float[1];
ZeroVal[0] = 0.0F;
// Allocate defaults.
AIL.MappAllocDefault(AIL.M_DEFAULT, ref AilApplication, ref AilSystem, ref AilDisplay, AIL.M_NULL, AIL.M_NULL);
// Allocate a display buffer and clear it.
AIL.MbufAlloc2d(AilSystem, IMAGE_WIDTH * 2, IMAGE_HEIGHT * 2, 8 + AIL.M_UNSIGNED, AIL.M_IMAGE + AIL.M_PROC + AIL.M_DISP, ref AilImage);
AIL.MbufClear(AilImage, 0L);
// Display the image buffer and prepare for overlay annotations.
AIL.MdispSelect(AilDisplay, AilImage);
AIL.MdispControl(AilDisplay, AIL.M_OVERLAY, AIL.M_ENABLE);
AIL.MdispInquire(AilDisplay, AIL.M_OVERLAY_ID, ref AilOverlayImage);
// Allocate child buffers in the 4 quadrants of the display image.
AIL.MbufChild2d(AilImage, 0, 0, IMAGE_WIDTH, IMAGE_HEIGHT, ref AilSubImage00);
AIL.MbufChild2d(AilImage, IMAGE_WIDTH, 0, IMAGE_WIDTH, IMAGE_HEIGHT, ref AilSubImage01);
AIL.MbufChild2d(AilImage, 0, IMAGE_HEIGHT, IMAGE_WIDTH, IMAGE_HEIGHT, ref AilSubImage10);
AIL.MbufChild2d(AilImage, IMAGE_WIDTH, IMAGE_HEIGHT, IMAGE_WIDTH, IMAGE_HEIGHT, ref AilSubImage11);
// Allocate processing buffers.
AIL.MbufAlloc2d(AilSystem, IMAGE_WIDTH, IMAGE_HEIGHT, 32 + AIL.M_FLOAT, AIL.M_IMAGE + AIL.M_PROC, ref AilTransformReal);
AIL.MbufAlloc2d(AilSystem, IMAGE_WIDTH, IMAGE_HEIGHT, 32 + AIL.M_FLOAT, AIL.M_IMAGE + AIL.M_PROC, ref AilTransformIm);
// Load a noisy image.
AIL.MbufLoad(NOISY_IMAGE, AilSubImage00);
// Print a message on the screen.
Console.Write("\nFFT:\n");
Console.Write("----\n\n");
Console.Write("The frequency spectrum of a noisy image will be computed to remove the periodic noise.\n");
Console.Write("Press any key to continue.\n\n");
Console.ReadKey(true);
// The image is Fourier transformed to obtain the magnitude of the
// spectrum. This result will be used to design the filter.
AIL.MimTransform(AilSubImage00, AIL.M_NULL, AilTransformReal, AilTransformIm, AIL.M_FFT, AIL.M_FORWARD + AIL.M_CENTER + AIL.M_MAGNITUDE + AIL.M_LOG_SCALE);
AIL.MbufCopy(AilTransformReal, AilSubImage10);
// Draw circles in the overlay around the points of interest.
AIL.MbufCopy(AilTransformReal, AilSubImage11);
AIL.MgraControl(AIL.M_DEFAULT, AIL.M_COLOR, AIL.M_COLOR_YELLOW);
AIL.MgraArc(AIL.M_DEFAULT, AilOverlayImage, X_NEGATIVE_FREQUENCY_POSITION, Y_FREQUENCY_POSITION + IMAGE_HEIGHT, CIRCLE_WIDTH, CIRCLE_WIDTH, 0, 360);
AIL.MgraArc(AIL.M_DEFAULT, AilOverlayImage, X_POSITIVE_FREQUENCY_POSITION, Y_FREQUENCY_POSITION + IMAGE_HEIGHT, CIRCLE_WIDTH, CIRCLE_WIDTH, 0, 360);
AIL.MgraArc(AIL.M_DEFAULT, AilOverlayImage, X_NEGATIVE_FREQUENCY_POSITION + IMAGE_WIDTH, Y_FREQUENCY_POSITION + IMAGE_HEIGHT, CIRCLE_WIDTH, CIRCLE_WIDTH, 0, 360);
AIL.MgraArc(AIL.M_DEFAULT, AilOverlayImage, X_POSITIVE_FREQUENCY_POSITION + IMAGE_WIDTH, Y_FREQUENCY_POSITION + IMAGE_HEIGHT, CIRCLE_WIDTH, CIRCLE_WIDTH, 0, 360);
// Put zero in the spectrum where the noise is located.
AIL.MbufPut2d(AilSubImage11, X_NEGATIVE_FREQUENCY_POSITION, Y_FREQUENCY_POSITION, 1, 1, ZeroVal);
AIL.MbufPut2d(AilSubImage11, X_POSITIVE_FREQUENCY_POSITION, Y_FREQUENCY_POSITION, 1, 1, ZeroVal);
// Compute the Fast Fourier Transform of the image.
AIL.MimTransform(AilSubImage00, AIL.M_NULL, AilTransformReal, AilTransformIm, AIL.M_FFT, AIL.M_FORWARD + AIL.M_CENTER);
// Filter the image in the frequency domain.
AIL.MbufPut2d(AilTransformReal, X_NEGATIVE_FREQUENCY_POSITION, Y_FREQUENCY_POSITION, 1, 1, ZeroVal);
AIL.MbufPut2d(AilTransformReal, X_POSITIVE_FREQUENCY_POSITION, Y_FREQUENCY_POSITION, 1, 1, ZeroVal);
AIL.MbufPut2d(AilTransformIm, X_NEGATIVE_FREQUENCY_POSITION, Y_FREQUENCY_POSITION, 1, 1, ZeroVal);
AIL.MbufPut2d(AilTransformIm, X_POSITIVE_FREQUENCY_POSITION, Y_FREQUENCY_POSITION, 1, 1, ZeroVal);
// Recover the image in the spatial domain.
AIL.MimTransform(AilTransformReal, AilTransformIm, AilSubImage01, AIL.M_NULL, AIL.M_FFT, AIL.M_REVERSE + AIL.M_CENTER + AIL.M_SATURATION);
// Print a message.
Console.Write("The frequency components of the noise are located in the center of the circles.\n");
Console.Write("The noise was removed by setting these frequency components to zero.\n");
Console.Write("Press any key to end.\n\n");
Console.ReadKey(true);
// Free buffers.
AIL.MbufFree(AilSubImage00);
AIL.MbufFree(AilSubImage01);
AIL.MbufFree(AilSubImage10);
AIL.MbufFree(AilSubImage11);
AIL.MbufFree(AilImage);
AIL.MbufFree(AilTransformReal);
AIL.MbufFree(AilTransformIm);
// Free defaults.
AIL.MappFreeDefault(AilApplication, AilSystem, AilDisplay, AIL.M_NULL, AIL.M_NULL);
}
}
}