IM: Other Domain Transform Operations

IM - An Imaging Tool

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Other Domain Transform Operations
[Image Processing]

Detailed Description

Hough, Distance.
See im_process_glo.h


Functions

int imProcessHoughLines (const imImage *src_image, imImage *dst_image)
int imProcessHoughLinesDraw (const imImage *src_image, const imImage *hough_points, imImage *dst_image)
void imProcessCrossCorrelation (const imImage *src_image1, const imImage *src_image2, imImage *dst_image)
void imProcessAutoCorrelation (const imImage *src_image, imImage *dst_image)
void imProcessDistanceTransform (const imImage *src_image, imImage *dst_image)
void imProcessRegionalMaximum (const imImage *src_image, imImage *dst_image)

Function Documentation

int imProcessHoughLines (  const imImage *  src_image,
imImage *  dst_image
) 
 

Hough Lines Transform.
It will detect white lines in a black background. So the source image must be a IM_BINARY image with the white lines of interest enhanced. The better the threshold with the white lines the better the line detection.
The destiny image must have IM_GRAY, IM_INT, width=180, height=2*rmax+1, where rmax is the image diagonal/2.
The houfh transform defines "cos(theta) * X + sin(theta) * Y = rho" and the parameters are in the interval:
theta = "0 .. 179", rho = "-height/2 .. height/2" .
Returns zero if the counter aborted.
Inspired from ideas in XITE, Copyright 1991, Blab, UiO
http://www.ifi.uio.no/~blab/Software/Xite/

im.ProcessHoughLines(src_image: imImage, dst_image: imImage) -> counter: boolean [in Lua 5] 
im.ProcessHoughLinesNew(image: imImage) -> counter: boolean, new_image: imImage [in Lua 5]

int imProcessHoughLinesDraw (  const imImage *  src_image,
const imImage *  hough_points,
imImage *  dst_image
) 
 

Draw detected hough lines.
The source image must be IM_GRAY and IM_BYTE. The destiny image can be a clone of the source image or it can be the source image for in place processing.
The hough points image is a hough transform image that was thresholded to a IM_BINARY image, usually using a Local Max threshold operation. Again the better the threshold the better the results.
The destiny image will be set to IM_MAP, and the detected lines will be drawn using a red color.
Returns the number of detected lines.

im.ProcessHoughLinesDraw(src_image: imImage, hough_points: imImage, dst_image: imImage) -> lines: number [in Lua 5] 
im.ProcessHoughLinesDrawNew(image: imImage, hough_points: imImage) -> lines: number, new_image: imImage [in Lua 5]

void imProcessCrossCorrelation (  const imImage *  src_image1,
const imImage *  src_image2,
imImage *  dst_image
) 
 

Calculates the Cross Correlation in the frequency domain.
CrossCorr(a,b) = IFFT(Conj(FFT(a))*FFT(b))
Images must be of the same size and only destiny image must be of type complex.

im.ProcessCrossCorrelation(src_image1: imImage, src_image2: imImage, dst_image: imImage) [in Lua 5] 
im.ProcessCrossCorrelationNew(image1: imImage, image2: imImage) -> new_image: imImage [in Lua 5]

void imProcessAutoCorrelation (  const imImage *  src_image,
imImage *  dst_image
) 
 

Calculates the Auto Correlation in the frequency domain.
Uses the cross correlation. Images must be of the same size and only destiny image must be of type complex.

im.ProcessAutoCorrelation(src_image: imImage, dst_image: imImage) [in Lua 5] 
im.ProcessAutoCorrelationNew(image: imImage) -> new_image: imImage [in Lua 5]

void imProcessDistanceTransform (  const imImage *  src_image,
imImage *  dst_image
) 
 

Calculates the Distance Transform of a binary image using an aproximation of the euclidian distance.
Each white pixel in the binary image is assigned a value equal to its distance from the nearest black pixel.
Uses a two-pass algorithm incrementally calculating the distance.
Source image must be IM_BINARY, destiny must be IM_FLOAT.

im.ProcessDistanceTransform(src_image: imImage, dst_image: imImage) [in Lua 5] 
im.ProcessDistanceTransformNew(image: imImage) -> new_image: imImage [in Lua 5]

void imProcessRegionalMaximum (  const imImage *  src_image,
imImage *  dst_image
) 
 

Marks all the regional maximum of the distance transform.
source is IMGRAY/IM_FLOAT destiny in IM_BINARY.
We consider maximum all connected pixel values that have smaller pixel values around it.

im.ProcessRegionalMaximum(src_image: imImage, dst_image: imImage) [in Lua 5] 
im.ProcessRegionalMaximumNew(image: imImage) -> new_image: imImage [in Lua 5]


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