Image::Leptonica::Func::warper
version 0.04
warper.c
warper.c High-level captcha interface PIX *pixSimpleCaptcha() Random sinusoidal warping PIX *pixRandomHarmonicWarp() Helper functions static l_float64 *generateRandomNumberArray() static l_int32 applyWarpTransform() Version using a LUT for sin PIX *pixRandomHarmonicWarpLUT() static l_int32 applyWarpTransformLUT() static l_int32 makeSinLUT() static l_float32 getSinFromLUT() Stereoscopic warping PIX *pixWarpStereoscopic() Linear and quadratic horizontal stretching PIX *pixStretchHorizontal() PIX *pixStretchHorizontalSampled() PIX *pixStretchHorizontalLI() Quadratic vertical shear PIX *pixQuadraticVShear() PIX *pixQuadraticVShearSampled() PIX *pixQuadraticVShearLI() Stereo from a pair of images PIX *pixStereoFromPair()
PIX * pixQuadraticVShear ( PIX *pixs, l_int32 dir, l_int32 vmaxt, l_int32 vmaxb, l_int32 operation, l_int32 incolor )
pixQuadraticVShear() Input: pixs (1, 8 or 32 bpp) dir (L_WARP_TO_LEFT or L_WARP_TO_RIGHT) vmaxt (max vertical displacement at edge and at top) vmaxb (max vertical displacement at edge and at bottom) operation (L_SAMPLED or L_INTERPOLATED) incolor (L_BRING_IN_WHITE or L_BRING_IN_BLACK) Return: pixd (stretched), or null on error Notes: (1) This gives a quadratic bending, upward or downward, as you move to the left or right. (2) If @dir == L_WARP_TO_LEFT, the right edge is unchanged, and the left edge pixels are moved maximally up or down. (3) Parameters @vmaxt and @vmaxb control the maximum amount of vertical pixel shear at the top and bottom, respectively. If @vmaxt > 0, the vertical displacement of pixels at the top is downward. Likewise, if @vmaxb > 0, the vertical displacement of pixels at the bottom is downward. (4) If @operation == L_SAMPLED, the dest pixels are taken from the nearest src pixel. Otherwise, we use linear interpolation between pairs of sampled pixels. (5) This is for quadratic shear. For uniform (linear) shear, use the standard shear operators.
PIX * pixQuadraticVShearLI ( PIX *pixs, l_int32 dir, l_int32 vmaxt, l_int32 vmaxb, l_int32 incolor )
pixQuadraticVShearLI() Input: pixs (8 or 32 bpp, or colormapped) dir (L_WARP_TO_LEFT or L_WARP_TO_RIGHT) vmaxt (max vertical displacement at edge and at top) vmaxb (max vertical displacement at edge and at bottom) incolor (L_BRING_IN_WHITE or L_BRING_IN_BLACK) Return: pixd (stretched), or null on error Notes: (1) See pixQuadraticVShear() for details.
PIX * pixQuadraticVShearSampled ( PIX *pixs, l_int32 dir, l_int32 vmaxt, l_int32 vmaxb, l_int32 incolor )
pixQuadraticVShearSampled() Input: pixs (1, 8 or 32 bpp) dir (L_WARP_TO_LEFT or L_WARP_TO_RIGHT) vmaxt (max vertical displacement at edge and at top) vmaxb (max vertical displacement at edge and at bottom) incolor (L_BRING_IN_WHITE or L_BRING_IN_BLACK) Return: pixd (stretched), or null on error Notes: (1) See pixQuadraticVShear() for details.
PIX * pixRandomHarmonicWarp ( PIX *pixs, l_float32 xmag, l_float32 ymag, l_float32 xfreq, l_float32 yfreq, l_int32 nx, l_int32 ny, l_uint32 seed, l_int32 grayval )
pixRandomHarmonicWarp() Input: pixs (8 bpp; no colormap) xmag, ymag (maximum magnitude of x and y distortion) xfreq, yfreq (maximum magnitude of x and y frequency) nx, ny (number of x and y harmonic terms) seed (of random number generator) grayval (color brought in from the outside; 0 for black, 255 for white) Return: pixd (8 bpp; no colormap), or null on error Notes: (1) To generate the warped image p(x',y'), set up the transforms that are in getWarpTransform(). For each (x',y') in the dest, the warp function computes the originating location (x, y) in the src. The differences (x - x') and (y - y') are given as a sum of products of sinusoidal terms. Each term is multiplied by a maximum amplitude (in pixels), and the angle is determined by a frequency and phase, and depends on the (x', y') value of the dest. Random numbers with a variable input seed are used to allow the warping to be unpredictable. A linear interpolation is used to find the value for the source at (x, y); this value is written into the dest. (2) This can be used to generate 'captcha's, which are somewhat randomly distorted images of text. A typical set of parameters for a captcha are: xmag = 4.0 ymag = 6.0 xfreq = 0.10 yfreq = 0.13 nx = 3 ny = 3 Other examples can be found in prog/warptest.c.
PIX * pixSimpleCaptcha ( PIX *pixs, l_int32 border, l_int32 nterms, l_uint32 seed, l_uint32 color, l_int32 cmapflag )
pixSimpleCaptcha() Input: pixs (8 bpp; no colormap) border (added white pixels on each side) nterms (number of x and y harmonic terms) seed (of random number generator) color (for colorizing; in 0xrrggbb00 format; use 0 for black) cmapflag (1 for colormap output; 0 for rgb) Return: pixd (8 bpp cmap or 32 bpp rgb), or null on error Notes: (1) This uses typical default values for generating captchas. The magnitudes of the harmonic warp are typically to be smaller when more terms are used, even though the phases are random. See, for example, prog/warptest.c.
PIX * pixStereoFromPair ( PIX *pix1, PIX *pix2, l_float32 rwt, l_float32 gwt, l_float32 bwt )
pixStereoFromPair() Input: pix1 (32 bpp rgb) pix2 (32 bpp rgb) rwt, gwt, bwt (weighting factors used for each component in pix1 to determine the output red channel) Return: pixd (stereo enhanced), or null on error Notes: (1) pix1 and pix2 are a pair of stereo images, ideally taken concurrently in the same plane, with some lateral translation. (2) The output red channel is determined from @pix1. The output green and blue channels are taken from the green and blue channels, respectively, of @pix2. (3) The weights determine how much of each component in @pix1 goes into the output red channel. The sum of weights must be 1.0. If it's not, we scale the weights to satisfy this criterion. (4) The most general pixel mapping allowed here is: rval = rwt * r1 + gwt * g1 + bwt * b1 (from pix1) gval = g2 (from pix2) bval = b2 (from pix2) (5) The simplest method is to use rwt = 1.0, gwt = 0.0, bwt = 0.0, but this causes unpleasant visual artifacts with red in the image. Use of green and blue from @pix1 in the red channel, instead of red, tends to fix that problem.
PIX * pixStretchHorizontal ( PIX *pixs, l_int32 dir, l_int32 type, l_int32 hmax, l_int32 operation, l_int32 incolor )
pixStretchHorizontal() Input: pixs (1, 8 or 32 bpp) dir (L_WARP_TO_LEFT or L_WARP_TO_RIGHT) type (L_LINEAR_WARP or L_QUADRATIC_WARP) hmax (horizontal displacement at edge) operation (L_SAMPLED or L_INTERPOLATED) incolor (L_BRING_IN_WHITE or L_BRING_IN_BLACK) Return: pixd (stretched/compressed), or null on error Notes: (1) If @hmax > 0, this is an increase in the coordinate value of pixels in pixd, relative to the same pixel in pixs. (2) If @dir == L_WARP_TO_LEFT, the pixels on the right edge of the image are not moved. So, for example, if @hmax > 0 and @dir == L_WARP_TO_LEFT, the pixels in pixd are contracted toward the right edge of the image, relative to those in pixs. (3) If @type == L_LINEAR_WARP, the pixel positions are moved to the left or right by an amount that varies linearly with the horizontal location. (4) If @operation == L_SAMPLED, the dest pixels are taken from the nearest src pixel. Otherwise, we use linear interpolation between pairs of sampled pixels.
PIX * pixStretchHorizontalLI ( PIX *pixs, l_int32 dir, l_int32 type, l_int32 hmax, l_int32 incolor )
pixStretchHorizontalLI() Input: pixs (1, 8 or 32 bpp) dir (L_WARP_TO_LEFT or L_WARP_TO_RIGHT) type (L_LINEAR_WARP or L_QUADRATIC_WARP) hmax (horizontal displacement at edge) incolor (L_BRING_IN_WHITE or L_BRING_IN_BLACK) Return: pixd (stretched/compressed), or null on error Notes: (1) See pixStretchHorizontal() for details.
PIX * pixStretchHorizontalSampled ( PIX *pixs, l_int32 dir, l_int32 type, l_int32 hmax, l_int32 incolor )
pixStretchHorizontalSampled() Input: pixs (1, 8 or 32 bpp) dir (L_WARP_TO_LEFT or L_WARP_TO_RIGHT) type (L_LINEAR_WARP or L_QUADRATIC_WARP) hmax (horizontal displacement at edge) incolor (L_BRING_IN_WHITE or L_BRING_IN_BLACK) Return: pixd (stretched/compressed), or null on error Notes: (1) See pixStretchHorizontal() for details.
PIX * pixWarpStereoscopic ( PIX *pixs, l_int32 zbend, l_int32 zshiftt, l_int32 zshiftb, l_int32 ybendt, l_int32 ybendb, l_int32 redleft )
pixWarpStereoscopic() Input: pixs (any depth, colormap ok) zbend (horizontal separation in pixels of red and cyan at the left and right sides, that gives rise to quadratic curvature out of the image plane) zshiftt (uniform pixel translation difference between red and cyan, that pushes the top of the image plane away from the viewer (zshiftt > 0) or towards the viewer (zshiftt < 0)) zshiftb (uniform pixel translation difference between red and cyan, that pushes the bottom of the image plane away from the viewer (zshiftb > 0) or towards the viewer (zshiftb < 0)) ybendt (multiplicative parameter for in-plane vertical displacement at the left or right edge at the top: y = ybendt * (2x/w - 1)^2 ) ybendb (same as ybendt, except at the left or right edge at the bottom) redleft (1 if the red filter is on the left; 0 otherwise) Return: pixd (32 bpp), or null on error Notes: (1) This function splits out the red channel, mucks around with it, then recombines with the unmolested cyan channel. (2) By using a quadratically increasing shift of the red pixels horizontally and away from the vertical centerline, the image appears to bend quadratically out of the image plane, symmetrically with respect to the vertical center line. A positive value of @zbend causes the plane to be curved away from the viewer. We use linearly interpolated stretching to avoid the appearance of kinks in the curve. (3) The parameters @zshiftt and @zshiftb tilt the image plane about a horizontal line through the center, and at the same time move that line either in toward the viewer or away. This is implemented by a combination of horizontal shear about the center line (for the tilt) and horizontal translation (to move the entire plane in or out). A positive value of @zshiftt moves the top of the plane away from the viewer, and a positive value of @zshiftb moves the bottom of the plane away. We use linear interpolated shear to avoid visible vertical steps in the tilted image. (4) The image can be bent in the plane and about the vertical centerline. The centerline does not shift, and the parameter @ybend gives the relative shift at left and right edges, with a downward shift for positive values of @ybend. (6) When writing out a steroscopic (red/cyan) image in jpeg, first call pixSetChromaSampling(pix, 0) to get sufficient resolution in the red channel. (7) Typical values are: zbend = 20 zshiftt = 15 zshiftb = -15 ybendt = 30 ybendb = 0 If the disparity z-values are too large, it is difficult for the brain to register the two images. (8) This function has been cleverly reimplemented by Jeff Breidenbach. The original implementation used two 32 bpp rgb images, and merged them at the end. The result is somewhat faded, and has a parameter "thresh" that controls the amount of color in the result. (The present implementation avoids these two problems, skipping both the colorization and the alpha blending at the end, and is about 3x faster) The basic operations with 32 bpp are as follows: // Immediate conversion to 32 bpp Pix *pixt1 = pixConvertTo32(pixs); // Do vertical shear Pix *pixr = pixQuadraticVerticalShear(pixt1, L_WARP_TO_RIGHT, ybendt, ybendb, L_BRING_IN_WHITE); // Colorize two versions, toward red and cyan Pix *pixc = pixCopy(NULL, pixr); l_int32 thresh = 150; // if higher, get less original color pixColorGray(pixr, NULL, L_PAINT_DARK, thresh, 255, 0, 0); pixColorGray(pixc, NULL, L_PAINT_DARK, thresh, 0, 255, 255); // Shift the red pixels; e.g., by stretching Pix *pixrs = pixStretchHorizontal(pixr, L_WARP_TO_RIGHT, L_QUADRATIC_WARP, zbend, L_INTERPOLATED, L_BRING_IN_WHITE); // Blend the shifted red and unshifted cyan 50:50 Pix *pixg = pixCreate(w, h, 8); pixSetAllArbitrary(pixg, 128); pixd = pixBlendWithGrayMask(pixrs, pixc, pixg, 0, 0);
Zakariyya Mughal <zmughal@cpan.org>
This software is copyright (c) 2014 by Zakariyya Mughal.
This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.
To install Image::Leptonica, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Image::Leptonica
CPAN shell
perl -MCPAN -e shell install Image::Leptonica
For more information on module installation, please visit the detailed CPAN module installation guide.