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Manual Reference Pages  -  IPA::GLOBAL (3)

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NAME

IPA::Global - methods that produce images where every pixel is a function of all pixels in the source image

CONTENTS

DESCRIPTION

Contains methods that produce images, where every pixel is a function of all pixels in the source image. The process can be described with the mapping function



   s = M(R)



where s is the pixel value in the output images, and R is the source image.
close_edges IMAGE [ gradient, maxlen, minedgelen, mingradient ] Closes edges of shapes on IMAGE, according to specified gradient image. The unclosed shapes converted to the closed if the gradient spot between the suspected dents falls under maxlen maximal length increment, mingradient the minimal gradient value and the edge is longer than minedgelen.

Supported types: Byte

Parameters:
gradient IMAGE Specifies the gradient image
maxlen INTEGER Maximal edge length
minedgelen INTEGER Minimal edge length
mingradient INTEGER Minimal gradient value

fill_holes IMAGE [ inPlace = 0, edgeSize = 1, backColor = 0, foreColor = 255, neighborhood = 4] Fills closed shapes to eliminate the contours with holes in IMAGE.

Supported types: Byte

Parameters:
inPlace BOOLEAN If true, the original image is changed
edgeSize INTEGER The edge breadth that is not touched by the algorithm
backColor INTEGER The pixel value used for determination whether a pixel belongs to the background.
foreColor INTEGER The pixel value used for hole filling.
neighborhood INTEGER Must be either 4 or 8. Selects whether the algorithm must assume 4- or 8- pixel connection.

area_filter IMAGE [ minArea = 0, maxArea = INT_MAX, inPlace = 0, edgeSize = 1, backColor = 0, foreColor = 255, neighborhood = 4] Identifies the objects on IMAGE and filters out these that have their area less than minArea and more than maxArea. The other parameters are identical to those passed to fill_holes.
identify_contours IMAGE [ edgeSize = 1, backColor = 0, foreColor = 255, neighborhood = 4] Identifies the objects on IMAGE and returns the contours as array of anonymous arrays of 4- or 8- connected pixel coordinates.

The parameters are identical to those passed to fill_holes.

Supported types: Byte

See also IPA::Region.

identify_scanlines IMAGE [ edgeSize = 1, backColor = 0, foreColor = 255, neighborhood = 4] Same as identify_contours but returns a set of scan lines.
identify_pixels IMAGE [ match => 0, eq => 0 ] Returns coordinates of all pixels that match (if eq is 1) or not match (eq is 0) color match.
fft IMAGE [ inverse = 0 ] Performs direct and inverse ( governed by inverse boolean flag ) fast Fourier transform. IMAGE must have dimensions of power of 2. The resulted image is always of DComplex type.

Supported types: all

fourier IMAGE [ inverse = 0 ] Performs direct and inverse ( governed by inverse boolean flag ) fast Fourier transform. If IMAGE dimensions not of power of 2, then IMAGE is scaled up to the closest power of 2, and the result is scaled back to the original dimensions.

The resulted image is always of DComplex type.

Supported types: all

band_filter IMAGE [ low = 0, spatial = 1, homomorph = 0, power = 2.0, cutoff = 20.0, boost = 0.7 ] Performs band filtering of IMAGE in frequency domain. IMAGE must have dimensions of power of 2. The resulted image is always of DComplex type.

Supported types: all

Parameters:
low BOOLEAN Boolean flag, indicates whether the low-pass or the high-pass is to be performed.
spatial BOOLEAN Boolean flag, indicates if IMAGE must be treated as if it is in the spatial domain, and therefore conversion to the frequency domain must be performed first.
homomorph BOOLEAN Boolean flag, indicates if the homomorph ( exponential ) equalization must be performed. Cannot be set to true if the image is in frequency domain ( if spatial parameter set to true ).
power FLOAT Power operator applied to the input frequency.
cutoff FLOAT Threshold value of the filter.
boost FLOAT Multiplication factor used in homomorph equalization.

butterworth IMAGE [ low = 0, spatial = 1, homomorph = 0, power = 2.0, cutoff = 20.0, boost = 0.7 ] Performs band filtering of IMAGE in frequency domain. If IMAGE dimensions not of power of 2, then IMAGE is scaled up to the closest power of 2, and the result is scaled back to the original dimensions.

The resulted image is always of DComplex type.

Supported types: all

The parameters are same as those passed to band_filter.

hough IMAGE [ type = ‘‘line’’, direct = 1, resolution = 500 ] Realizes Hough transform. If type is line, linear transform is performed. With direct transform, resolution is width of the resulted image.

Note: Returns a 8-bit grayscale image, which means that for all practical purposes the image shouldn’t possibly contain more than 256 line candidates.

Supported types: all

hough2lines IMAGE [ width = 1000, height = 1000 ] Takes a Hough-transformed image, where each pixel is a line. For each non-zero pixel a line projection on a rectangle with given width and height is calculated. Returns array of quad values in format [x0,y0,x1,y2] where the coordinates stand for the start and the end of a line.

So, if the direct transform was called as



   $h = hough( $i );



then plotting lines back (after $h was filtered) would be



   $i-> line(@$_) for @{ hough2lines( $h,
        width  => $i-> width,
        height => $i-> height
   ) };



Supported types: 8-bit (expects result from hough function).

    Optimized plotting

The following functions can draw lines on images, and are optimized for speed, because Prima doesn’t support drawing on images outside begin_paint/end_paint scope.
bar IMAGE, X1, Y1, X2, Y2, COLOR Fill the given rectangular area with COLOR.
hlines IMAGE, OFFSET_X, OFFSET_Y, LINES, COLOR Draws set of horizontal lines as defined by LINES with COLOR. LINES is an array of triplet integers, where each contains [X1, X2, Y] coordinates - beginning of hline, end of hline, and vline.
line IMAGE, X1, Y1, X2, Y2, COLOR Draws a single line from X1,Y1 to X2,Y2 .
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