Image::Leptonica::Func::scalelow
version 0.04
scalelow.c
scalelow.c Color (interpolated) scaling: general case void scaleColorLILow() Grayscale (interpolated) scaling: general case void scaleGrayLILow() Color (interpolated) scaling: 2x upscaling void scaleColor2xLILow() void scaleColor2xLILineLow() Grayscale (interpolated) scaling: 2x upscaling void scaleGray2xLILow() void scaleGray2xLILineLow() Grayscale (interpolated) scaling: 4x upscaling void scaleGray4xLILow() void scaleGray4xLILineLow() Grayscale and color scaling by closest pixel sampling l_int32 scaleBySamplingLow() Color and grayscale downsampling with (antialias) lowpass filter l_int32 scaleSmoothLow() void scaleRGBToGray2Low() Color and grayscale downsampling with (antialias) area mapping l_int32 scaleColorAreaMapLow() l_int32 scaleGrayAreaMapLow() l_int32 scaleAreaMapLow2() Binary scaling by closest pixel sampling l_int32 scaleBinaryLow() Scale-to-gray 2x void scaleToGray2Low() l_uint32 *makeSumTabSG2() l_uint8 *makeValTabSG2() Scale-to-gray 3x void scaleToGray3Low() l_uint32 *makeSumTabSG3() l_uint8 *makeValTabSG3() Scale-to-gray 4x void scaleToGray4Low() l_uint32 *makeSumTabSG4() l_uint8 *makeValTabSG4() Scale-to-gray 6x void scaleToGray6Low() l_uint8 *makeValTabSG6() Scale-to-gray 8x void scaleToGray8Low() l_uint8 *makeValTabSG8() Scale-to-gray 16x void scaleToGray16Low() Grayscale mipmap l_int32 scaleMipmapLow()
l_uint32 * makeSumTabSG2 ( void )
makeSumTabSG2() Returns a table of 256 l_uint32s, giving the four output 8-bit grayscale sums corresponding to 8 input bits of a binary image, for a 2x scale-to-gray op. The sums from two adjacent scanlines are then added and transformed to output four 8 bpp pixel values, using makeValTabSG2().
l_uint32 * makeSumTabSG3 ( void )
makeSumTabSG3() Returns a table of 64 l_uint32s, giving the two output 8-bit grayscale sums corresponding to 6 input bits of a binary image, for a 3x scale-to-gray op. In practice, this would be used three times (on adjacent scanlines), and the sums would be added and then transformed to output 8 bpp pixel values, using makeValTabSG3().
l_uint32 * makeSumTabSG4 ( void )
makeSumTabSG4() Returns a table of 256 l_uint32s, giving the two output 8-bit grayscale sums corresponding to 8 input bits of a binary image, for a 4x scale-to-gray op. The sums from four adjacent scanlines are then added and transformed to output 8 bpp pixel values, using makeValTabSG4().
l_uint8 * makeValTabSG2 ( void )
makeValTabSG2() Returns an 8 bit value for the sum of ON pixels in a 2x2 square, according to val = 255 - (255 * sum)/4 where sum is in set {0,1,2,3,4}
l_uint8 * makeValTabSG3 ( void )
makeValTabSG3() Returns an 8 bit value for the sum of ON pixels in a 3x3 square, according to val = 255 - (255 * sum)/9 where sum is in set {0, ... ,9}
l_uint8 * makeValTabSG4 ( void )
makeValTabSG4() Returns an 8 bit value for the sum of ON pixels in a 4x4 square, according to val = 255 - (255 * sum)/16 where sum is in set {0, ... ,16}
l_uint8 * makeValTabSG6 ( void )
makeValTabSG6() Returns an 8 bit value for the sum of ON pixels in a 6x6 square, according to val = 255 - (255 * sum)/36 where sum is in set {0, ... ,36}
l_uint8 * makeValTabSG8 ( void )
makeValTabSG8() Returns an 8 bit value for the sum of ON pixels in an 8x8 square, according to val = 255 - (255 * sum)/64 where sum is in set {0, ... ,64}
void scaleAreaMapLow2 ( l_uint32 *datad, l_int32 wd, l_int32 hd, l_int32 wpld, l_uint32 *datas, l_int32 d, l_int32 wpls )
scaleAreaMapLow2() Note: This function is called with either 8 bpp gray or 32 bpp RGB. The result is a 2x reduced dest.
l_int32 scaleBinaryLow ( l_uint32 *datad, l_int32 wd, l_int32 hd, l_int32 wpld, l_uint32 *datas, l_int32 ws, l_int32 hs, l_int32 wpls )
scaleBinaryLow() Notes: (1) The dest must be cleared prior to this operation, and we clear it here in the low-level code. (2) We reuse dest pixels and dest pixel rows whenever possible for upscaling; downscaling is done by strict subsampling.
l_int32 scaleBySamplingLow ( l_uint32 *datad, l_int32 wd, l_int32 hd, l_int32 wpld, l_uint32 *datas, l_int32 ws, l_int32 hs, l_int32 d, l_int32 wpls )
scaleBySamplingLow() Notes: (1) The dest must be cleared prior to this operation, and we clear it here in the low-level code. (2) We reuse dest pixels and dest pixel rows whenever possible. This speeds the upscaling; downscaling is done by strict subsampling and is unaffected. (3) Because we are sampling and not interpolating, this routine works directly, without conversion to full RGB color, for 2, 4 or 8 bpp palette color images.
void scaleColor2xLILineLow ( l_uint32 *lined, l_int32 wpld, l_uint32 *lines, l_int32 ws, l_int32 wpls, l_int32 lastlineflag )
scaleColor2xLILineLow() Input: lined (ptr to top destline, to be made from current src line) wpld lines (ptr to current src line) ws wpls lastlineflag (1 if last src line; 0 otherwise) Return: void *** Warning: implicit assumption about RGB component ordering
void scaleColor2xLILow ( l_uint32 *datad, l_int32 wpld, l_uint32 *datas, l_int32 ws, l_int32 hs, l_int32 wpls )
scaleColor2xLILow() This is a special case of 2x expansion by linear interpolation. Each src pixel contains 4 dest pixels. The 4 dest pixels in src pixel 1 are numbered at their UL corners. The 4 dest pixels in src pixel 1 are related to that src pixel and its 3 neighboring src pixels as follows: 1-----2-----|-----|-----| | | | | | | | | | | src 1 --> 3-----4-----| | | <-- src 2 | | | | | | | | | | |-----|-----|-----|-----| | | | | | | | | | | src 3 --> | | | | | <-- src 4 | | | | | | | | | | |-----|-----|-----|-----| dest src ---- --- dp1 = sp1 dp2 = (sp1 + sp2) / 2 dp3 = (sp1 + sp3) / 2 dp4 = (sp1 + sp2 + sp3 + sp4) / 4 We iterate over the src pixels, and unroll the calculation for each set of 4 dest pixels corresponding to that src pixel, caching pixels for the next src pixel whenever possible. The method is exactly analogous to the one we use for scaleGray2xLILow() and its line version. P3 speed is about 5 x 10^7 dst pixels/sec/GHz
void scaleColorAreaMapLow ( l_uint32 *datad, l_int32 wd, l_int32 hd, l_int32 wpld, l_uint32 *datas, l_int32 ws, l_int32 hs, l_int32 wpls )
scaleColorAreaMapLow() This should only be used for downscaling. We choose to divide each pixel into 16 x 16 sub-pixels. This is much slower than scaleSmoothLow(), but it gives a better representation, esp. for downscaling factors between 1.5 and 5. All src pixels are subdivided into 256 sub-pixels, and are weighted by the number of sub-pixels covered by the dest pixel. This is about 2x slower than scaleSmoothLow(), but the results are significantly better on small text.
void scaleColorLILow ( l_uint32 *datad, l_int32 wd, l_int32 hd, l_int32 wpld, l_uint32 *datas, l_int32 ws, l_int32 hs, l_int32 wpls )
scaleColorLILow() We choose to divide each pixel into 16 x 16 sub-pixels. Linear interpolation is equivalent to finding the fractional area (i.e., number of sub-pixels divided by 256) associated with each of the four nearest src pixels, and weighting each pixel value by this fractional area. P3 speed is about 7 x 10^6 dst pixels/sec/GHz
void scaleGray2xLILineLow ( l_uint32 *lined, l_int32 wpld, l_uint32 *lines, l_int32 ws, l_int32 wpls, l_int32 lastlineflag )
scaleGray2xLILineLow() Input: lined (ptr to top destline, to be made from current src line) wpld lines (ptr to current src line) ws wpls lastlineflag (1 if last src line; 0 otherwise) Return: void
void scaleGray2xLILow ( l_uint32 *datad, l_int32 wpld, l_uint32 *datas, l_int32 ws, l_int32 hs, l_int32 wpls )
scaleGray2xLILow() This is a special case of 2x expansion by linear interpolation. Each src pixel contains 4 dest pixels. The 4 dest pixels in src pixel 1 are numbered at their UL corners. The 4 dest pixels in src pixel 1 are related to that src pixel and its 3 neighboring src pixels as follows: 1-----2-----|-----|-----| | | | | | | | | | | src 1 --> 3-----4-----| | | <-- src 2 | | | | | | | | | | |-----|-----|-----|-----| | | | | | | | | | | src 3 --> | | | | | <-- src 4 | | | | | | | | | | |-----|-----|-----|-----| dest src ---- --- dp1 = sp1 dp2 = (sp1 + sp2) / 2 dp3 = (sp1 + sp3) / 2 dp4 = (sp1 + sp2 + sp3 + sp4) / 4 We iterate over the src pixels, and unroll the calculation for each set of 4 dest pixels corresponding to that src pixel, caching pixels for the next src pixel whenever possible.
void scaleGray4xLILineLow ( l_uint32 *lined, l_int32 wpld, l_uint32 *lines, l_int32 ws, l_int32 wpls, l_int32 lastlineflag )
scaleGray4xLILineLow() Input: lined (ptr to top destline, to be made from current src line) wpld lines (ptr to current src line) ws wpls lastlineflag (1 if last src line; 0 otherwise) Return: void
void scaleGray4xLILow ( l_uint32 *datad, l_int32 wpld, l_uint32 *datas, l_int32 ws, l_int32 hs, l_int32 wpls )
scaleGray4xLILow() This is a special case of 4x expansion by linear interpolation. Each src pixel contains 16 dest pixels. The 16 dest pixels in src pixel 1 are numbered at their UL corners. The 16 dest pixels in src pixel 1 are related to that src pixel and its 3 neighboring src pixels as follows: 1---2---3---4---|---|---|---|---| | | | | | | | | | 5---6---7---8---|---|---|---|---| | | | | | | | | | src 1 --> 9---a---b---c---|---|---|---|---| <-- src 2 | | | | | | | | | d---e---f---g---|---|---|---|---| | | | | | | | | | |===|===|===|===|===|===|===|===| | | | | | | | | | |---|---|---|---|---|---|---|---| | | | | | | | | | src 3 --> |---|---|---|---|---|---|---|---| <-- src 4 | | | | | | | | | |---|---|---|---|---|---|---|---| | | | | | | | | | |---|---|---|---|---|---|---|---| dest src ---- --- dp1 = sp1 dp2 = (3 * sp1 + sp2) / 4 dp3 = (sp1 + sp2) / 2 dp4 = (sp1 + 3 * sp2) / 4 dp5 = (3 * sp1 + sp3) / 4 dp6 = (9 * sp1 + 3 * sp2 + 3 * sp3 + sp4) / 16 dp7 = (3 * sp1 + 3 * sp2 + sp3 + sp4) / 8 dp8 = (3 * sp1 + 9 * sp2 + 1 * sp3 + 3 * sp4) / 16 dp9 = (sp1 + sp3) / 2 dp10 = (3 * sp1 + sp2 + 3 * sp3 + sp4) / 8 dp11 = (sp1 + sp2 + sp3 + sp4) / 4 dp12 = (sp1 + 3 * sp2 + sp3 + 3 * sp4) / 8 dp13 = (sp1 + 3 * sp3) / 4 dp14 = (3 * sp1 + sp2 + 9 * sp3 + 3 * sp4) / 16 dp15 = (sp1 + sp2 + 3 * sp3 + 3 * sp4) / 8 dp16 = (sp1 + 3 * sp2 + 3 * sp3 + 9 * sp4) / 16 We iterate over the src pixels, and unroll the calculation for each set of 16 dest pixels corresponding to that src pixel, caching pixels for the next src pixel whenever possible.
void scaleGrayAreaMapLow ( l_uint32 *datad, l_int32 wd, l_int32 hd, l_int32 wpld, l_uint32 *datas, l_int32 ws, l_int32 hs, l_int32 wpls )
scaleGrayAreaMapLow() This should only be used for downscaling. We choose to divide each pixel into 16 x 16 sub-pixels. This is about 2x slower than scaleSmoothLow(), but the results are significantly better on small text, esp. for downscaling factors between 1.5 and 5. All src pixels are subdivided into 256 sub-pixels, and are weighted by the number of sub-pixels covered by the dest pixel.
void scaleGrayLILow ( l_uint32 *datad, l_int32 wd, l_int32 hd, l_int32 wpld, l_uint32 *datas, l_int32 ws, l_int32 hs, l_int32 wpls )
scaleGrayLILow() We choose to divide each pixel into 16 x 16 sub-pixels. Linear interpolation is equivalent to finding the fractional area (i.e., number of sub-pixels divided by 256) associated with each of the four nearest src pixels, and weighting each pixel value by this fractional area.
l_int32 scaleMipmapLow ( l_uint32 *datad, l_int32 wd, l_int32 hd, l_int32 wpld, l_uint32 *datas1, l_int32 wpls1, l_uint32 *datas2, l_int32 wpls2, l_float32 red )
scaleMipmapLow() See notes in scale.c for pixScaleToGrayMipmap(). This function is here for pedagogical reasons. It gives poor results on document images because of aliasing.
void scaleRGBToGray2Low ( l_uint32 *datad, l_int32 wd, l_int32 hd, l_int32 wpld, l_uint32 *datas, l_int32 wpls, l_float32 rwt, l_float32 gwt, l_float32 bwt )
scaleRGBToGray2Low() Notes: (1) This function is called with 32 bpp RGB src and 8 bpp, half-resolution dest. The weights should add to 1.0.
l_int32 scaleSmoothLow ( l_uint32 *datad, l_int32 wd, l_int32 hd, l_int32 wpld, l_uint32 *datas, l_int32 ws, l_int32 hs, l_int32 d, l_int32 wpls, l_int32 size )
scaleSmoothLow() Notes: (1) This function is called on 8 or 32 bpp src and dest images. (2) size is the full width of the lowpass smoothing filter. It is correlated with the reduction ratio, being the nearest integer such that size is approximately equal to hs / hd.
void scaleToGray16Low ( l_uint32 *datad, l_int32 wd, l_int32 hd, l_int32 wpld, l_uint32 *datas, l_int32 wpls, l_int32 *tab8 )
scaleToGray16Low() Input: usual image variables tab8 (made from makePixelSumTab8()) Return: 0 if OK; 1 on error. The output is processed one dest byte at a time, corresponding to 16 rows consisting each of 2 src bytes in the input image. This uses one lookup table, tab8, which gives the sum of ON pixels in a byte. After summing for all ON pixels in the 32 src bytes, which is between 0 and 256, this is converted to an 8 bpp grayscale value between 0 (for 255 or 256 bits ON) and 255 (for 0 bits ON).
void scaleToGray2Low ( l_uint32 *datad, l_int32 wd, l_int32 hd, l_int32 wpld, l_uint32 *datas, l_int32 wpls, l_uint32 *sumtab, l_uint8 *valtab )
scaleToGray2Low() Input: usual image variables sumtab (made from makeSumTabSG2()) valtab (made from makeValTabSG2()) Return: 0 if OK; 1 on error. The output is processed in sets of 4 output bytes on a row, corresponding to 4 2x2 bit-blocks in the input image. Two lookup tables are used. The first, sumtab, gets the sum of ON pixels in 4 sets of two adjacent bits, storing the result in 4 adjacent bytes. After sums from two rows have been added, the second table, valtab, converts from the sum of ON pixels in the 2x2 block to an 8 bpp grayscale value between 0 (for 4 bits ON) and 255 (for 0 bits ON).
void scaleToGray3Low ( l_uint32 *datad, l_int32 wd, l_int32 hd, l_int32 wpld, l_uint32 *datas, l_int32 wpls, l_uint32 *sumtab, l_uint8 *valtab )
scaleToGray3Low() Input: usual image variables sumtab (made from makeSumTabSG3()) valtab (made from makeValTabSG3()) Return: 0 if OK; 1 on error Each set of 8 3x3 bit-blocks in the source image, which consist of 72 pixels arranged 24 pixels wide by 3 scanlines, is converted to a row of 8 8-bit pixels in the dest image. These 72 pixels of the input image are runs of 24 pixels in three adjacent scanlines. Each run of 24 pixels is stored in the 24 LSbits of a 32-bit word. We use 2 LUTs. The first, sumtab, takes 6 of these bits and stores sum, taken 3 bits at a time, in two bytes. (See makeSumTabSG3). This is done for each of the 3 scanlines, and the results are added. We now have the sum of ON pixels in the first two 3x3 blocks in two bytes. The valtab LUT then converts these values (which go from 0 to 9) to grayscale values between between 255 and 0. (See makeValTabSG3). This process is repeated for each of the other 3 sets of 6x3 input pixels, giving 8 output pixels in total. Note: because the input image is processed in groups of 24 x 3 pixels, the process clips the input height to (h - h % 3) and the input width to (w - w % 24).
void scaleToGray4Low ( l_uint32 *datad, l_int32 wd, l_int32 hd, l_int32 wpld, l_uint32 *datas, l_int32 wpls, l_uint32 *sumtab, l_uint8 *valtab )
scaleToGray4Low() Input: usual image variables sumtab (made from makeSumTabSG4()) valtab (made from makeValTabSG4()) Return: 0 if OK; 1 on error. The output is processed in sets of 2 output bytes on a row, corresponding to 2 4x4 bit-blocks in the input image. Two lookup tables are used. The first, sumtab, gets the sum of ON pixels in two sets of four adjacent bits, storing the result in 2 adjacent bytes. After sums from four rows have been added, the second table, valtab, converts from the sum of ON pixels in the 4x4 block to an 8 bpp grayscale value between 0 (for 16 bits ON) and 255 (for 0 bits ON).
void scaleToGray6Low ( l_uint32 *datad, l_int32 wd, l_int32 hd, l_int32 wpld, l_uint32 *datas, l_int32 wpls, l_int32 *tab8, l_uint8 *valtab )
scaleToGray6Low() Input: usual image variables tab8 (made from makePixelSumTab8()) valtab (made from makeValTabSG6()) Return: 0 if OK; 1 on error Each set of 4 6x6 bit-blocks in the source image, which consist of 144 pixels arranged 24 pixels wide by 6 scanlines, is converted to a row of 4 8-bit pixels in the dest image. These 144 pixels of the input image are runs of 24 pixels in six adjacent scanlines. Each run of 24 pixels is stored in the 24 LSbits of a 32-bit word. We use 2 LUTs. The first, tab8, takes 6 of these bits and stores sum in one byte. This is done for each of the 6 scanlines, and the results are added. We now have the sum of ON pixels in the first 6x6 block. The valtab LUT then converts these values (which go from 0 to 36) to grayscale values between between 255 and 0. (See makeValTabSG6). This process is repeated for each of the other 3 sets of 6x6 input pixels, giving 4 output pixels in total. Note: because the input image is processed in groups of 24 x 6 pixels, the process clips the input height to (h - h % 6) and the input width to (w - w % 24).
void scaleToGray8Low ( l_uint32 *datad, l_int32 wd, l_int32 hd, l_int32 wpld, l_uint32 *datas, l_int32 wpls, l_int32 *tab8, l_uint8 *valtab )
scaleToGray8Low() Input: usual image variables tab8 (made from makePixelSumTab8()) valtab (made from makeValTabSG8()) Return: 0 if OK; 1 on error. The output is processed one dest byte at a time, corresponding to 8 rows of src bytes in the input image. Two lookup tables are used. The first, tab8, gets the sum of ON pixels in a byte. After sums from 8 rows have been added, the second table, valtab, converts from this value (which is between 0 and 64) to an 8 bpp grayscale value between 0 (for all 64 bits ON) and 255 (for 0 bits ON).
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.
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cpanm
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