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/* IM 3 sample that calculates the Forward FFT,
process in the domain frequency,
and calculates the Inverse FFT.
Needs "im.lib" and "im_fftw.lib".
Usage: proc_fourier <input_file_name> <output_file_name> <output_format>
Example: proc_fourier test.tif test_proc.tif TIFF
*/
#include <im.h>
#include <im_image.h>
#include <im_process.h>
#include <im_convert.h>
#include <im_complex.h>
#include <stdio.h>
void FreqDomainProc(imImage* fft_image)
{
// a loop for all the color planes
for (int d = 0; d < fft_image->depth; d++)
{
imcfloat* data = (imcfloat*)fft_image->data[d];
for (int y = 0; y < fft_image->height; y++)
{
for (int x = 0; x < fft_image->width; x++)
{
// Do something
// Remeber that the zero frequency is at the center
int offset = y * fft_image->width + x;
data[offset].imag = 0; // notice in the result that the imaginary part has an important hole.
}
}
}
}
void PrintError(int error)
{
switch (error)
{
case IM_ERR_OPEN:
printf("Error Opening File.\n");
break;
case IM_ERR_MEM:
printf("Insuficient memory.\n");
break;
case IM_ERR_ACCESS:
printf("Error Accessing File.\n");
break;
case IM_ERR_DATA:
printf("Image type not Suported.\n");
break;
case IM_ERR_FORMAT:
printf("Invalid Format.\n");
break;
case IM_ERR_COMPRESS:
printf("Invalid or unsupported compression.\n");
break;
default:
printf("Unknown Error.\n");
}
}
imImage* LoadImage(const char* file_name)
{
int error;
imFile* ifile = imFileOpen(file_name, &error);
if (!ifile)
{
PrintError(error);
return 0;
}
imImage* image = imFileLoadImage(ifile, 0, &error); // load the first image in the file.
if (!image)
PrintError(error);
imFileClose(ifile);
return image;
}
void SaveImage(imImage* image, const char* file_name, const char* format)
{
int error;
imFile* ifile = imFileNew(file_name, format, &error);
if (!ifile)
{
PrintError(error);
return;
}
error = imFileSaveImage(ifile, image);
if (error != IM_ERR_NONE)
PrintError(error);
imFileClose(ifile);
}
int main(int argc, char* argv[])
{
if (argc < 4)
{
printf("Invalid number of arguments.\n");
return 0;
}
// Loads the image from file
imImage* image = LoadImage(argv[1]);
if (!image)
return 0;
// Creates a new image similar of the original but with complex data type.
// FFTW does not requires that the image size is a power of 2.
imImage* fft_image = imImageCreate(image->width, image->height, image->color_space, IM_CFLOAT);
if (!image)
return 0;
// Forward FFT
imProcessFFTW(image, fft_image);
// The user processing
FreqDomainProc(fft_image);
// The inverse is still a complex image
imImage* ifft_image = imImageClone(fft_image);
if (!image)
return 0;
// Inverse FFT
imProcessIFFTW(fft_image, ifft_image);
// Converts the complex image to the same type of the original image
// so we can reuse its buffer
// (usually will be a bitmap image so we can also view the result)
if (image->data_type != IM_CFLOAT)
{
// This function will scan for min and max values before converting the data type
// There wiil be no gamma conversion, use abssolute values, and only the real part will be considered.
imConvertDataType(ifft_image, image, IM_CPX_REAL, IM_GAMMA_LINEAR, 1, IM_CAST_MINMAX);
}
SaveImage(image, argv[2], argv[3]);
imImageDestroy(image);
imImageDestroy(fft_image);
imImageDestroy(ifft_image);
return 1;
}
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