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Leptonica 1.68
C Image Processing Library
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Leptonica 1.68
C Image Processing Library
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Basic operations on image kernels for convolution; special kernels. More...
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Basic operations on image kernels for convolution; special kernels.
Basic operations on kernels for image convolution Create/destroy/copy L_KERNEL *kernelCreate() void kernelDestroy() L_KERNEL *kernelCopy() Accessors: l_int32 kernelGetElement() l_int32 kernelSetElement() l_int32 kernelGetParameters() l_int32 kernelSetOrigin() l_int32 kernelGetSum() l_int32 kernelGetMinMax() Normalize/invert L_KERNEL *kernelNormalize() L_KERNEL *kernelInvert() Helper function l_float32 **create2dFloatArray() Serialized I/O L_KERNEL *kernelRead() L_KERNEL *kernelReadStream() l_int32 kernelWrite() l_int32 kernelWriteStream() Making a kernel from a compiled string L_KERNEL *kernelCreateFromString() Making a kernel from a simple file format L_KERNEL *kernelCreateFromFile() Making a kernel from a Pix L_KERNEL *kernelCreateFromPix() Display a kernel in a pix PIX *kernelDisplayInPix() Parse string to extract numbers NUMA *parseStringForNumbers() Simple parametric kernels L_KERNEL *makeFlatKernel() L_KERNEL *makeGaussianKernel() L_KERNEL *makeGaussianKernelSep() L_KERNEL *makeDoGKernel()
Definition in file kernel.c.
Input: height, width Return: kernel, or null on error
Notes: (1) kernelCreate() initializes all values to 0. (2) After this call, (cy,cx) and nonzero data values must be assigned.
Definition at line 91 of file kernel.c.
References CALLOC, create2dFloatArray(), L_Kernel::data, ERROR_PTR, NULL, PROCNAME, L_Kernel::sx, and L_Kernel::sy.
Referenced by kernelCopy(), kernelCreateFromFile(), kernelCreateFromPix(), kernelCreateFromString(), kernelInvert(), kernelNormalize(), kernelReadStream(), main(), makeDoGKernel(), makeFlatKernel(), and makeGaussianKernel().
| void kernelDestroy | ( | L_KERNEL ** | pkel | ) |
Input: &kel (<to be="" nulled>="">) Return: void
Definition at line 116 of file kernel.c.
References L_Kernel::data, FREE, L_WARNING, NULL, PROCNAME, and L_Kernel::sy.
Referenced by fpixConvolve(), fpixConvolveSep(), main(), pixConvolve(), and pixConvolveSep().
Input: kels (source kernel) Return: keld (copy of kels), or null on error
Definition at line 147 of file kernel.c.
References L_Kernel::cx, L_Kernel::cy, L_Kernel::data, ERROR_PTR, kernelCreate(), kernelGetParameters(), NULL, and PROCNAME.
Referenced by fpixConvolve(), kernelNormalize(), and pixConvolve().
Input: kel row col &val Return: 0 if OK; 1 on error
Definition at line 183 of file kernel.c.
References L_Kernel::data, ERROR_INT, PROCNAME, L_Kernel::sx, and L_Kernel::sy.
Referenced by kernelDisplayInPix(), and pixMultMatrixColor().
Input: kernel row col val Return: 0 if OK; 1 on error
Definition at line 215 of file kernel.c.
References L_Kernel::data, ERROR_INT, PROCNAME, L_Kernel::sx, and L_Kernel::sy.
Referenced by kernelCreateFromFile(), kernelCreateFromPix(), kernelCreateFromString(), main(), makeDoGKernel(), makeFlatKernel(), and makeGaussianKernel().
| l_int32 kernelGetParameters | ( | L_KERNEL * | kel, |
| l_int32 * | psy, | ||
| l_int32 * | psx, | ||
| l_int32 * | pcy, | ||
| l_int32 * | pcx | ||
| ) |
Input: kernel &sy, &sx, &cy, &cx (<optional return>="">; each can be null) Return: 0 if OK, 1 on error
Definition at line 242 of file kernel.c.
References L_Kernel::cx, L_Kernel::cy, ERROR_INT, PROCNAME, L_Kernel::sx, and L_Kernel::sy.
Referenced by fpixConvolve(), kernelCopy(), kernelDisplayInPix(), kernelGetMinMax(), kernelGetSum(), kernelInvert(), kernelNormalize(), kernelWriteStream(), pixConvolve(), and pixMultMatrixColor().
Input: kernel cy, cx Return: 0 if OK; 1 on error
Definition at line 272 of file kernel.c.
References L_Kernel::cx, L_Kernel::cy, ERROR_INT, and PROCNAME.
Referenced by kernelCreateFromFile(), kernelCreateFromPix(), kernelCreateFromString(), kernelReadStream(), main(), makeDoGKernel(), makeFlatKernel(), and makeGaussianKernel().
Input: kernel &sum (<return> sum of all kernel values) Return: 0 if OK, 1 on error
Definition at line 294 of file kernel.c.
References L_Kernel::data, ERROR_INT, kernelGetParameters(), NULL, and PROCNAME.
Referenced by kernelNormalize(), and main().
Input: kernel &min (<optional return>=""> minimum value) &max (<optional return>=""> maximum value) Return: 0 if OK, 1 on error
Definition at line 326 of file kernel.c.
References L_Kernel::data, ERROR_INT, kernelGetParameters(), NULL, and PROCNAME.
Referenced by kernelDisplayInPix().
Input: kels (source kel, to be normalized) normsum (desired sum of elements in keld) Return: keld (normalized version of kels), or null on error or if sum of elements is very close to 0)
Notes: (1) If the sum of kernel elements is close to 0, do not try to calculate the normalized kernel. Instead, return a copy of the input kernel, with an error message.
Definition at line 380 of file kernel.c.
References L_Kernel::cx, L_Kernel::cy, L_Kernel::data, ERROR_PTR, kernelCopy(), kernelCreate(), kernelGetParameters(), kernelGetSum(), L_ABS, L_ERROR, NULL, and PROCNAME.
Referenced by fpixConvolve(), fpixConvolveSep(), pixConvolve(), and pixConvolveSep().
Input: kels (source kel, to be inverted) Return: keld (spatially inverted, about the origin), or null on error
Notes: (1) For convolution, the kernel is spatially inverted before a "correlation" operation is done between the kernel and the image.
Definition at line 424 of file kernel.c.
References L_Kernel::cx, L_Kernel::cy, L_Kernel::data, ERROR_PTR, kernelCreate(), kernelGetParameters(), NULL, and PROCNAME.
Referenced by fpixConvolve(), and pixConvolve().
Input: sy (rows == height) sx (columns == width) Return: doubly indexed array (i.e., an array of sy row pointers, each of which points to an array of sx floats)
Notes: (1) The array[sy][sx] is indexed in standard "matrix notation", with the row index first.
Definition at line 464 of file kernel.c.
References CALLOC, ERROR_PTR, NULL, and PROCNAME.
Referenced by kernelCreate().
| L_KERNEL* kernelRead | ( | const char * | fname | ) |
Input: filename Return: kernel, or null on error
Definition at line 494 of file kernel.c.
References ERROR_PTR, fopenReadStream(), kernelReadStream(), NULL, and PROCNAME.
Referenced by main().
| L_KERNEL* kernelReadStream | ( | FILE * | fp | ) |
Input: stream Return: kernel, or null on error
Definition at line 521 of file kernel.c.
References L_Kernel::data, ERROR_PTR, KERNEL_VERSION_NUMBER, kernelCreate(), kernelSetOrigin(), NULL, PROCNAME, and version.
Referenced by kernelRead().
Input: fname (output file) kernel Return: 0 if OK, 1 on error
Definition at line 564 of file kernel.c.
References ERROR_INT, fopenWriteStream(), kernelWriteStream(), NULL, and PROCNAME.
Referenced by main().
Input: stream kel Return: 0 if OK, 1 on error
Definition at line 593 of file kernel.c.
References L_Kernel::data, ERROR_INT, KERNEL_VERSION_NUMBER, kernelGetParameters(), and PROCNAME.
Referenced by kernelWrite().
| L_KERNEL* kernelCreateFromString | ( | l_int32 | h, |
| l_int32 | w, | ||
| l_int32 | cy, | ||
| l_int32 | cx, | ||
| const char * | kdata | ||
| ) |
Input: height, width cy, cx (origin) kdata Return: kernel of the given size, or null on error
Notes: (1) The data is an array of chars, in row-major order, giving space separated integers in the range [-255 ... 255]. (2) The only other formatting limitation is that you must leave space between the last number in each row and the double-quote. If possible, it's also nice to have each line in the string represent a line in the kernel; e.g., static const char *kdata = " 20 50 20 " " 70 140 70 " " 20 50 20 ";
Definition at line 643 of file kernel.c.
References ERROR_PTR, kernelCreate(), kernelSetElement(), kernelSetOrigin(), NULL, numaDestroy(), numaGetCount(), numaGetFValue(), parseStringForNumbers(), and PROCNAME.
Referenced by main().
| L_KERNEL* kernelCreateFromFile | ( | const char * | filename | ) |
Input: filename Return: kernel, or null on error
Notes: (1) The file contains, in the following order:
Definition at line 724 of file kernel.c.
References ERROR_PTR, FREE, kernelCreate(), kernelSetElement(), kernelSetOrigin(), l_binaryRead(), L_NOCOPY, NULL, numaCreate(), numaDestroy(), numaGetCount(), numaGetFValue(), numaJoin(), parseStringForNumbers(), PROCNAME, sarrayCreateLinesFromString(), sarrayDestroy(), sarrayGetCount(), sarrayGetString(), and size.
Referenced by main().
Input: pix cy, cx (origin of kernel) Return: kernel, or null on error
Notes: (1) The origin must be positive and within the dimensions of the pix.
Definition at line 812 of file kernel.c.
References ERROR_PTR, kernelCreate(), kernelSetElement(), kernelSetOrigin(), NULL, pixGetDimensions(), pixGetPixel(), and PROCNAME.
Referenced by main().
Input: kernel size (of grid interiors; odd; minimum size of 17 is enforced) gthick (grid thickness; minimum size of 2 is enforced) Return: pix (display of kernel), or null on error
Notes: (1) This gives a visual representation of a kernel. (2) The origin is outlined in red.
Definition at line 859 of file kernel.c.
References ERROR_PTR, kernelGetElement(), kernelGetMinMax(), kernelGetParameters(), L_ABS, L_FLIP_PIXELS, L_MAX, L_SET_PIXELS, L_WARNING, NULL, PIX_DST, PIX_NOT, pixCreate(), pixDestroy(), pixPaintThroughMask(), pixRasterop(), pixRenderLine(), pixSetAll(), pixSetMaskedGeneral(), PROCNAME, x0, and y0.
Referenced by main().
| NUMA* parseStringForNumbers | ( | const char * | str, |
| const char * | seps | ||
| ) |
Input: string (containing numbers; not changed) seps (string of characters that can be used between ints) Return: numa (of numbers found), or null on error
Note: (1) The numbers can be ints or floats.
Definition at line 953 of file kernel.c.
References ERROR_PTR, FREE, NULL, numaAddNumber(), numaCreate(), PROCNAME, stringNew(), and strtokSafe().
Referenced by kernelCreateFromFile(), kernelCreateFromString(), and pixThresholdGrayArb().
Input: height, width cy, cx (origin of kernel) Return: kernel, or null on error
Notes: (1) This is the same low-pass filtering kernel that is used in the block convolution functions. (2) The kernel origin (, ) is typically placed as near the center of the kernel as possible. If height and width are odd, then using cy = (height - 1) / 2 and cx = (width - 1) / 2 places the origin at the exact center. (3) This returns a normalized kernel.
Definition at line 1002 of file kernel.c.
References ERROR_PTR, kernelCreate(), kernelSetElement(), kernelSetOrigin(), NULL, and PROCNAME.
Referenced by main().
| L_KERNEL* makeGaussianKernel | ( | l_int32 | halfheight, |
| l_int32 | halfwidth, | ||
| l_float32 | stdev, | ||
| l_float32 | max | ||
| ) |
Input: halfheight, halfwidth (sx = 2 * halfwidth + 1, etc) stdev (standard deviation) max (value at (cx,cy)) Return: kernel, or null on error
Notes: (1) The kernel size (sx, sy) = (2 * halfwidth + 1, 2 * halfheight + 1). (2) The kernel center (cx, cy) = (halfwidth, halfheight). (3) The halfwidth and halfheight are typically equal, and are typically several times larger than the standard deviation. (4) If pixConvolve() is invoked with normalization (the sum of kernel elements = 1.0), use 1.0 for max (or any number that's not too small or too large).
Definition at line 1045 of file kernel.c.
References ERROR_PTR, kernelCreate(), kernelSetElement(), kernelSetOrigin(), NULL, and PROCNAME.
Referenced by main(), and makeGaussianKernelSep().
| l_int32 makeGaussianKernelSep | ( | l_int32 | halfheight, |
| l_int32 | halfwidth, | ||
| l_float32 | stdev, | ||
| l_float32 | max, | ||
| L_KERNEL ** | pkelx, | ||
| L_KERNEL ** | pkely | ||
| ) |
Input: halfheight, halfwidth (sx = 2 * halfwidth + 1, etc) stdev (standard deviation) max (value at (cx,cy)) &kelx (<return> x part of kernel) &kely (<return> y part of kernel) Return: 0 if OK, 1 on error
Notes: (1) See makeGaussianKernel() for description of input parameters. (2) These kernels are constructed so that the result of both normalized and un-normalized convolution will be the same as when convolving with pixConvolve() using the full kernel. (3) The trick for the un-normalized convolution is to have the product of the two kernel elemets at (cx,cy) be equal to max, not max**2. That's why the max for kely is 1.0. If instead we use sqrt(max) for both, the results are slightly less accurate, when compared to using the full kernel in makeGaussianKernel().
Definition at line 1097 of file kernel.c.
References ERROR_INT, makeGaussianKernel(), and PROCNAME.
Referenced by main().
Input: halfheight, halfwidth (sx = 2 * halfwidth + 1, etc) stdev (standard deviation) ratio (of stdev for wide filter to stdev for narrow one) Return: kernel, or null on error
Notes: (1) The DoG (difference of gaussians) is a wavelet mother function with null total sum. By subtracting two blurred versions of the image, it acts as a bandpass filter for frequencies passed by the narrow gaussian but stopped by the wide one.See: http://en.wikipedia.org/wiki/Difference_of_Gaussians (2) The kernel size (sx, sy) = (2 * halfwidth + 1, 2 * halfheight + 1). (3) The kernel center (cx, cy) = (halfwidth, halfheight). (4) The halfwidth and halfheight are typically equal, and are typically several times larger than the standard deviation. (5) The ratio is the ratio of standard deviations of the wide to narrow gaussian. It must be >= 1.0; 1.0 is a no-op. (6) Because the kernel is a null sum, it must be invoked without normalization in pixConvolve().
Definition at line 1140 of file kernel.c.
References ERROR_PTR, kernelCreate(), kernelSetElement(), kernelSetOrigin(), NULL, and PROCNAME.
Referenced by main().
1.7.3 
