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quadtree.c Top level quadtree linear statistics l_int32 pixQuadtreeMean() l_int32 pixQuadtreeVariance() Statistics in an arbitrary rectangle l_int32 pixMeanInRectangle() l_int32 pixVarianceInRectangle() Quadtree regions BOXAA *boxaaQuadtreeRegions() Quadtree access l_int32 quadtreeGetParent() l_int32 quadtreeGetChildren() l_int32 quadtreeMaxLevels() Display quadtree PIX *fpixaDisplayQuadtree() There are many other statistical quantities that can be computed in a quadtree, such as rank values, and these can be added as the need arises. Similar results that can approximate a single level of the quadtree can be generated by pixGetAverageTiled(). There we specify the tile size over which the mean, mean square, and root variance are generated; the results are saved in a (reduced size) pix. Because the tile dimensions are integers, it is usually not possible to obtain tilings that are a power of 2, as required for quadtrees.
BOXAA * boxaaQuadtreeRegions ( l_int32 w, l_int32 h, l_int32 nlevels )
boxaaQuadtreeRegions() Input: w, h (of pix that is being quadtree-ized) nlevels (in quadtree) Return: baa (for quadtree regions at each level), or null on error Notes: (1) The returned boxaa has @nlevels of boxa, each containing the set of rectangles at that level. The rectangle at level 0 is the entire region; at level 1 the region is divided into 4 rectangles, and at level n there are n^4 rectangles. (2) At each level, the rectangles in the boxa are in "raster" order, with LR (fast scan) and TB (slow scan).
PIX * fpixaDisplayQuadtree ( FPIXA *fpixa, l_int32 factor )
fpixaDisplayQuadtree() Input: fpixa (mean, variance or root variance) factor (replication factor at lowest level) Return: pixd (8 bpp, mosaic of quadtree images), or null on error Notes: (1) The mean and root variance fall naturally in the 8 bpp range, but the variance is typically outside the range. This function displays 8 bpp pix clipped to 255, so the image pixels will mostly be 255 (white).
l_int32 pixMeanInRectangle ( PIX *pixs, BOX *box, PIX *pixma, l_float32 *pval )
pixMeanInRectangle() Input: pix (8 bpp) box (region to compute mean value) pixma (mean accumulator) &val (<return> mean value Return: 0 if OK, 1 on error Notes: (1) This function is intended to be used for many rectangles on the same image. It can find the mean within a rectangle in O(1), independent of the size of the rectangle.
l_int32 pixQuadtreeMean ( PIX *pixs, l_int32 nlevels, PIX *pix_ma, FPIXA **pfpixa )
pixQuadtreeMean() Input: pixs (8 bpp, no colormap) nlevels (in quadtree; max allowed depends on image size) *pix_ma (input mean accumulator; can be null) *pfpixa (<return> mean values in quadtree) Return: 0 if OK, 1 on error Notes: (1) The returned fpixa has @nlevels of fpix, each containing the mean values at its level. Level 0 has a single value; level 1 has 4 values; level 2 has 16; etc.
l_int32 pixQuadtreeVariance ( PIX *pixs, l_int32 nlevels, PIX *pix_ma, DPIX *dpix_msa, FPIXA **pfpixa_v, FPIXA **pfpixa_rv )
pixQuadtreeVariance() Input: pixs (8 bpp, no colormap) nlevels (in quadtree) *pix_ma (input mean accumulator; can be null) *dpix_msa (input mean square accumulator; can be null) *pfpixa_v (<optional return> variance values in quadtree) *pfpixa_rv (<optional return> root variance values in quadtree) Return: 0 if OK, 1 on error Notes: (1) The returned fpixav and fpixarv have @nlevels of fpix, each containing at the respective levels the variance and root variance values.
l_int32 pixVarianceInRectangle ( PIX *pixs, BOX *box, PIX *pix_ma, DPIX *dpix_msa, l_float32 *pvar, l_float32 *prvar )
pixVarianceInRectangle() Input: pix (8 bpp) box (region to compute variance and/or root variance) pix_ma (mean accumulator) dpix_msa (mean square accumulator) &var (<optional return> variance) &rvar (<optional return> root variance) Return: 0 if OK, 1 on error Notes: (1) This function is intended to be used for many rectangles on the same image. It can find the variance and/or the square root of the variance within a rectangle in O(1), independent of the size of the rectangle.
l_int32 quadtreeGetChildren ( FPIXA *fpixa, l_int32 level, l_int32 x, l_int32 y, l_float32 *pval00, l_float32 *pval10, l_float32 *pval01, l_float32 *pval11 )
quadtreeGetChildren() Input: fpixa (mean, variance or root variance) level, x, y (of current pixel) &val00, val01, val10, val11 (<return> child pixel values) Return: 0 if OK, 1 on error Notes: (1) Check return value for error. On error, all return vals are 0.0. (2) The returned child pixels are located at: level + 1 (2x, 2y), (2x+1, 2y), (2x, 2y+1), (2x+1, 2y+1)
l_int32 quadtreeGetParent ( FPIXA *fpixa, l_int32 level, l_int32 x, l_int32 y, l_float32 *pval )
quadtreeGetParent() Input: fpixa (mean, variance or root variance) level, x, y (of current pixel) &val (<return> parent pixel value), or 0.0 on error. Return: 0 if OK, 1 on error Notes: (1) Check return value for error. On error, val is returned as 0.0. (2) The parent is located at: level - 1 (x/2, y/2)
l_int32 quadtreeMaxLevels ( l_int32 w, l_int32 h )
quadtreeMaxLevels() Input: w, h (of image) Return: maxlevels (maximum number of levels allowed), or -1 on error Notes: (1) The criterion for maxlevels is that the subdivision not go down below the single pixel level. The 1.5 factor is intended to keep any rectangle from accidentally having zero dimension due to integer truncation.
Zakariyya Mughal <email@example.com>
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.