Available in LEADTOOLS Imaging Pro, Vector, Document, and Medical Imaging toolkits. |
#include "ltwrappr.h"
virtual L_INT LBitmap::DFT (pFTArray, prcRange, uFlags)
pFTARRAY pFTArray; |
/* pointer to a structure */ |
RECT * prcRange; |
/* pointer to range rectangle */ |
L_UINT uFlags; |
/* flags */ |
Computes the Discrete Fourier transform of an image or the Inverse Discrete Fourier transform as specified in the uFlags parameter.
Parameter |
Description |
|
pFTArray |
Pointer to an FTARRAY structure. The acxData member of the FTARRAY structure is a two-dimensional array that holds the frequency components of the image. Its size must be the same as the image. This array is filled by the function when DFT_DFT flag has been chosen, and it must be sent to the function to construct the image from it when DFT_IDFT flag has been chosen. |
|
prcRange |
Specifies the frequency range to be computed when DFT_DFT flag is chosen. It specifies the frequency range that will be used in the image construction when DFT_IDFT is chosen. The left value refers to the minimum X harmonic, the right refers to the maximum X harmonic, the top refers to the minimum Y harmonic and the bottom refers to the maximum Y harmonic. The maximum X harmonic equals (Width 1) and the maximum Y harmonic equals (Height 1). The minimum X harmonic equals 0 and the minimum Y harmonic equals 0 |
|
uFlags |
Flags that indicate the transformation type, operation channel, frequency data type used to reconstruct the image, the clipping type, the used or computed frequencies range, the operation on the specified X harmonics range, and the operation on the specified Y harmonics range. You can use a bitwise OR (|) to specify one flag from each group. |
|
|
The following flags represent the transformation type: |
|
|
Value |
Meaning |
|
DFT_DFT |
[0x0000001] Convert the image into frequency domain and store the results in the acxData. |
|
DFT_IDFT |
[0x0000002] Construct an image using the frequency components from acxData. This option will change the values of acxData. |
|
The following flags represent the operation channel type: |
|
|
Value |
Meaning |
|
DFT_BLUE |
[0x0000010] Use the blue channel. |
|
DFT_GREEN |
[0x0000020] Use the green channel. |
|
DFT_RED |
[0x0000030] Use the red channel. |
|
DFT_GRAY |
[0x0000040] Use the master channel. If this flag is combined with FFT_IFFT, the reconstructed image will be gray. |
|
The following flags represent the frequency data type used for constructing the image. This flag is used only if DFT_IDFT is set and will be ignored if DFT_DFT is set: |
|
|
Value |
Meaning |
|
DFT_IDFT_MAG |
[0x0000100] Construct the image from the frequency magnitude data only. |
|
DFT_IDFT_PHS |
[0x0000200] Construct the image from frequency phase data only. |
|
DFT_IDFT_BOTH |
[0x0000300] Construct the image from both magnitude and phase data. |
|
The following flags represent the clipping type. This flag is used only if DFT_IDFT is set and ignored if DFT_DFT is set: |
|
|
Value |
Meaning |
|
DFT_IDFT_CLIP |
[0x0001000] Clip the constructed image values so they are between 0 and 255. |
|
DFT_IDFT_SCL |
[0x0002000] Scale the constructed image values so they are between 0 and 255. |
|
The following flags represent which harmonics are used: |
|
|
Value |
Meaning |
|
DFT_ALL |
[0x0010000] Use or compute all harmonics. If this flag is used the range rectangle and the range flags will be ignored. |
|
DFT_RANGE |
[0x0020000] Use or compute the harmonics specified in the range rectangle. |
|
The following flags represent the operations on the X Harmonics range: |
|
|
Value |
Meaning |
|
DFT_INSIDE_X |
[0x0100000] Use or compute only X harmonics inside the X range and ignore those outside the range. |
|
DFT_OUTSIDE_X |
[0x0200000] Use or compute only the X harmonics outside the X range and ignore those inside the range. |
|
The following flags represent the operations on the Y Harmonics range: |
|
|
Value |
Meaning |
|
DFT_INSIDE_Y |
[0x1000000] Use or compute only Y harmonics inside the Y range and ignore those outside the range. |
|
DFT_OUTSIDE_Y |
[0x2000000] Use or compute only the Y harmonics outside the Y range and ignore those inside the range. |
Returns
SUCCESS |
The function was successful. |
< 1 |
An error occurred. Refer to Return Codes. |
Comments
This function converts the image from the time domain to the frequency domain and vice versa using the Discrete Fourier Transform algorithm. Use the LBitmap::FFT to use a Fast Fourier Transform algorithm on a bitmap. Please note however, that this function does not impose the size restrictions (the width and height having to be powers of 2) that the Fast Fourier Transform function, LBitmap::FFT, imposes upon bitmaps.
Before using this function, you need to use the LBitmap::AllocFTArray function to allocate a FTARRAY structure large enough to hold Fourier Transform coefficients for pBitmap. When you are finished, you should free the allocated array by calling the LBitmap::FreeFTArray function.
This function does not work on regions. If a bitmap has a region the function ignores it and processes the entire bitmap.
To update a status bar or detect a user interrupt during execution of this function, refer to LBase::EnableStatusCallback.
This function does not support 12 and 16-bit grayscale and 48 and 64-bit color images. If the image is 12 and 16-bit grayscale and 48 and 64-bit color, the function will not return an error.
This function does not support 32-bit grayscale images. It returns the error code ERROR_GRAY32_UNSUPPORTED if a 32-bit grayscale image is passed to this function.
Required DLLs and Libraries
LTIMGCOR For a listing of the exact DLLs and Libraries needed, based on the toolkit version, refer to Files To Be Included With Your Application. |
Win32, x64.
See Also
Example
L_INT LBitmap__DFTExample(LBitmap *pLeadBitmap) { L_INT nRet; /* This example loads a bitmap and applies DFT function. */ RECT rcRange; pFTARRAY pFTArray; /*Allocate FT buffer*/ nRet =pLeadBitmap->AllocFTArray (&pFTArray, sizeof(FTARRAY)); if(nRet !=SUCCESS) return nRet; rcRange.left = 0; rcRange.right = pLeadBitmap->GetWidth () / 4; rcRange.top = 0; rcRange.bottom = pLeadBitmap->GetHeight () / 2; /* Apply DFT*/ nRet =pLeadBitmap->DFT(pFTArray, &rcRange, DFT_DFT | DFT_GRAY | DFT_RANGE| DFT_INSIDE_X| DFT_OUTSIDE_Y); if(nRet !=SUCCESS) return nRet; /* : : Free FT buffer */ nRet =LBitmap::FreeFTArray (pFTArray); if(nRet !=SUCCESS) return nRet; return SUCCESS; }