Leptonica
1.54
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#define EQUAL_SIZE_WARNING 0 |
static BOXA * findTileRegionsForSearch | ( | BOX * | box, |
l_int32 | w, | ||
l_int32 | h, | ||
l_int32 | searchdir, | ||
l_int32 | mindist, | ||
l_int32 | tsize, | ||
l_int32 | ntiles | ||
) | [static] |
Input: box (region of Pix to search around) w, h (dimensions of Pix) searchdir (L_HORIZ or L_VERT; direction to search) mindist (min distance of selected tile edge from box; >= 0) tsize (tile size; > 1; even; typically ~50) ntiles (number of tiles tested in each row/column) Return: boxa if OK, or null on error
Notes: (1) See calling function pixfindRepCloseTile().
l_int32* makePixelCentroidTab8 | ( | void | ) |
Input: void Return: table of 256 l_int32, or null on error
Notes: (1) This table of integers gives the centroid weight of the 1 bits in the 8 bit index. In other words, if sumtab is obtained by makePixelSumTab8, and centroidtab is obtained by makePixelCentroidTab8, then, for 1 <= i <= 255, centroidtab[i] / (float)sumtab[i] is the centroid of the 1 bits in the 8-bit index i, where the MSB is considered to have position 0 and the LSB is considered to have position 7.
l_int32* makePixelSumTab8 | ( | void | ) |
Input: void Return: table of 256 l_int32, or null on error
Notes: (1) This table of integers gives the number of 1 bits in the 8 bit index.
NUMA* pixAbsDiffByColumn | ( | PIX * | pix, |
BOX * | box | ||
) |
Input: pix (8 bpp; no colormap) box (<optional> clipping box for region; can be null) Return: na of abs val pixel difference averages by column, or null on error
Notes: (1) This is an average over differences of adjacent pixels along each column. (2) To resample for a bin size different from 1, use numaUniformSampling() on the result of this function.
NUMA* pixAbsDiffByRow | ( | PIX * | pix, |
BOX * | box | ||
) |
Input: pix (8 bpp; no colormap) box (<optional> clipping box for region; can be null) Return: na of abs val pixel difference averages by row, or null on error
Notes: (1) This is an average over differences of adjacent pixels along each row. (2) To resample for a bin size different from 1, use numaUniformSampling() on the result of this function.
Input: pix (8 bpp; not cmapped) box (<optional> if null, use entire image) dir (differences along L_HORIZONTAL_LINE or L_VERTICAL_LINE) &absdiff (<return> average of abs diff pixel values in region) Return: 0 if OK; 1 on error
Notes: (1) This gives the average over the abs val of differences of adjacent pixels values, along either each row: dir == L_HORIZONTAL_LINE column: dir == L_VERTICAL_LINE
l_int32 pixAbsDiffOnLine | ( | PIX * | pix, |
l_int32 | x1, | ||
l_int32 | y1, | ||
l_int32 | x2, | ||
l_int32 | y2, | ||
l_float32 * | pabsdiff | ||
) |
Input: pix (8 bpp; not cmapped) x1, y1 (first point; x1 <= x2, y1 <= y2) x2, y2 (first point) &absdiff (<return> average of abs diff pixel values on line) Return: 0 if OK; 1 on error
Notes: (1) This gives the average over the abs val of differences of adjacent pixels values, along a line that is either horizontal or vertical. (2) If horizontal, require x1 < x2; if vertical, require y1 < y2.
NUMA* pixaCountPixels | ( | PIXA * | pixa | ) |
Input: pixa (array of 1 bpp pix) Return: na of ON pixels in each pix, or null on error
Input: pixd (<optional>; this can be null, equal to pixs1, different from pixs1) pixs1 (can be == pixd) pixs2 (must be != pixd) Return: pixd always
Notes: (1) This gives the intersection of two images with equal depth, aligning them to the the UL corner. pixs1 and pixs2 need not have the same width and height. (2) There are 3 cases: (a) pixd == null, (src1 & src2) --> new pixd (b) pixd == pixs1, (src1 & src2) --> src1 (in-place) (c) pixd != pixs1, (src1 & src2) --> input pixd (3) For clarity, if the case is known, use these patterns: (a) pixd = pixAnd(NULL, pixs1, pixs2); (b) pixAnd(pixs1, pixs1, pixs2); (c) pixAnd(pixd, pixs1, pixs2); (4) The size of the result is determined by pixs1. (5) The depths of pixs1 and pixs2 must be equal. (6) Note carefully that the order of pixs1 and pixs2 only matters for the in-place case. For in-place, you must have pixd == pixs1. Setting pixd == pixs2 gives an incorrect result: the copy puts pixs1 image data in pixs2, and the rasterop is then between pixs2 and pixs2 (a no-op).
NUMA* pixAverageByColumn | ( | PIX * | pix, |
BOX * | box, | ||
l_int32 | type | ||
) |
Input: pix (8 or 16 bpp; no colormap) box (<optional> clipping box for sum; can be null) type (L_WHITE_IS_MAX, L_BLACK_IS_MAX) Return: na of pixel averages by column, or null on error
Notes: (1) To resample for a bin size different from 1, use numaUniformSampling() on the result of this function. (2) If type == L_BLACK_IS_MAX, black pixels get the maximum value (0xff for 8 bpp, 0xffff for 16 bpp) and white get 0.
NUMA* pixAverageByRow | ( | PIX * | pix, |
BOX * | box, | ||
l_int32 | type | ||
) |
Input: pix (8 or 16 bpp; no colormap) box (<optional> clipping box for sum; can be null) type (L_WHITE_IS_MAX, L_BLACK_IS_MAX) Return: na of pixel averages by row, or null on error
Notes: (1) To resample for a bin size different from 1, use numaUniformSampling() on the result of this function. (2) If type == L_BLACK_IS_MAX, black pixels get the maximum value (0xff for 8 bpp, 0xffff for 16 bpp) and white get 0.
l_int32 pixAverageInRect | ( | PIX * | pix, |
BOX * | box, | ||
l_float32 * | pave | ||
) |
Input: pix (1, 2, 4, 8 bpp; not cmapped) box (<optional> if null, use entire image) &ave (<return> average of pixel values in region) Return: 0 if OK; 1 on error
l_int32 pixCombineMasked | ( | PIX * | pixd, |
PIX * | pixs, | ||
PIX * | pixm | ||
) |
Input: pixd (1 bpp, 8 bpp gray or 32 bpp rgb; no cmap) pixs (1 bpp, 8 bpp gray or 32 bpp rgb; no cmap) pixm (<optional> 1 bpp mask; no operation if NULL) Return: 0 if OK; 1 on error
Notes: (1) In-place operation; pixd is changed. (2) This sets each pixel in pixd that co-locates with an ON pixel in pixm to the corresponding value of pixs. (3) pixs and pixd must be the same depth and not colormapped. (4) All three input pix are aligned at the UL corner, and the operation is clipped to the intersection of all three images. (5) If pixm == NULL, it's a no-op. (6) Implementation: see notes in pixCombineMaskedGeneral(). For 8 bpp selective masking, you might guess that it would be faster to generate an 8 bpp version of pixm, using pixConvert1To8(pixm, 0, 255), and then use a general combine operation d = (d & ~m) | (s & m) on a word-by-word basis. Not always. The word-by-word combine takes a time that is independent of the mask data. If the mask is relatively sparse, the byte-check method is actually faster!
Input: pixd (1 bpp, 8 bpp gray or 32 bpp rgb) pixs (1 bpp, 8 bpp gray or 32 bpp rgb) pixm (<optional> 1 bpp mask) x, y (origin of pixs and pixm relative to pixd; can be negative) Return: 0 if OK; 1 on error
Notes: (1) In-place operation; pixd is changed. (2) This is a generalized version of pixCombinedMasked(), where the source and mask can be placed at the same (arbitrary) location relative to pixd. (3) pixs and pixd must be the same depth and not colormapped. (4) The UL corners of both pixs and pixm are aligned with the point (x, y) of pixd, and the operation is clipped to the intersection of all three images. (5) If pixm == NULL, it's a no-op. (6) Implementation. There are two ways to do these. In the first, we use rasterop, ORing the part of pixs under the mask with pixd (which has been appropriately cleared there first). In the second, the mask is used one pixel at a time to selectively replace pixels of pixd with those of pixs. Here, we use rasterop for 1 bpp and pixel-wise replacement for 8 and 32 bpp. To use rasterop for 8 bpp, for example, we must first generate an 8 bpp version of the mask. The code is simple:
Pix *pixm8 = pixConvert1To8(NULL, pixm, 0, 255); Pix *pixt = pixAnd(NULL, pixs, pixm8); pixRasterop(pixd, x, y, wmin, hmin, PIX_DST & PIX_NOT(PIX_SRC), pixm8, 0, 0); pixRasterop(pixd, x, y, wmin, hmin, PIX_SRC | PIX_DST, pixt, 0, 0); pixDestroy(&pixt); pixDestroy(&pixm8);
Input: pixs (8 bpp, or colormapped) box (<optional>) over which count is made; use entire image null) val (pixel value to count) factor (subsampling factor; integer >= 1) &count (<return> count; estimate it if factor > 1) Return: na (histogram), or null on error
Notes: (1) If pixs is cmapped, is compared to the colormap index; otherwise, is compared to the grayscale value. (2) Set the subsampling > 1 to reduce the amount of computation. If > 1, multiply the count by * .
NUMA* pixCountByColumn | ( | PIX * | pix, |
BOX * | box | ||
) |
Input: pix (1 bpp) box (<optional> clipping box for count; can be null) Return: na of number of ON pixels by column, or null on error
Notes: (1) To resample for a bin size different from 1, use numaUniformSampling() on the result of this function.
NUMA* pixCountByRow | ( | PIX * | pix, |
BOX * | box | ||
) |
Input: pix (1 bpp) box (<optional> clipping box for count; can be null) Return: na of number of ON pixels by row, or null on error
Notes: (1) To resample for a bin size different from 1, use numaUniformSampling() on the result of this function.
l_int32 pixCountPixels | ( | PIX * | pix, |
l_int32 * | pcount, | ||
l_int32 * | tab8 | ||
) |
Input: pix (1 bpp) &count (<return> count of ON pixels) tab8 (<optional> 8-bit pixel lookup table) Return: 0 if OK; 1 on error
NUMA* pixCountPixelsByColumn | ( | PIX * | pix | ) |
Input: pix (1 bpp) Return: na of counts in each column, or null on error
NUMA* pixCountPixelsByRow | ( | PIX * | pix, |
l_int32 * | tab8 | ||
) |
Input: pix (1 bpp) tab8 (<optional> 8-bit pixel lookup table) Return: na of counts, or null on error
Input: pix (1 bpp) row number &count (<return> sum of ON pixels in raster line) tab8 (<optional> 8-bit pixel lookup table) Return: 0 if OK; 1 on error
l_int32 pixFindRepCloseTile | ( | PIX * | pixs, |
BOX * | box, | ||
l_int32 | searchdir, | ||
l_int32 | mindist, | ||
l_int32 | tsize, | ||
l_int32 | ntiles, | ||
BOX ** | pboxtile, | ||
l_int32 | debug | ||
) |
Input: pixs (32 bpp rgb) box (region of pixs to search around) searchdir (L_HORIZ or L_VERT; direction to search) mindist (min distance of selected tile edge from box; >= 0) tsize (tile size; > 1; even; typically ~50) ntiles (number of tiles tested in each row/column) &boxtile (<return> region of best tile) debug (1 for debug output) Return: 0 if OK, 1 on error
Notes: (1) This looks for one or two square tiles with conforming median intensity and low variance, that is outside but near the input box. (2) specifies the gap between the box and the potential tiles. The tiles are given an overlap of 50%. specifies the number of tiles that are tested beyond for each row or column. (3) For example, if = 20, = 50 and = 3, a horizontal search to the right will have 3 tiles in each row, with left edges at 20, 45 and 70 from the right edge of the input . The number of rows of tiles is determined by the height of and , with the 50% overlap..
l_int32 pixForegroundFraction | ( | PIX * | pix, |
l_float32 * | pfract | ||
) |
Input: pix (1 bpp) &fract (<return> fraction of ON pixels) Return: 0 if OK; 1 on error
l_int32 pixGetColorNearMaskBoundary | ( | PIX * | pixs, |
PIX * | pixm, | ||
BOX * | box, | ||
l_int32 | dist, | ||
l_uint32 * | pval, | ||
l_int32 | debug | ||
) |
Input: pixs (32 bpp rgb) pixm (1 bpp mask, full image) box (region of mask; typically b.b. of a component) dist (distance into BG from mask boundary to use) &pval (<return> average pixel value) debug (1 to output mask images) Return: 0 if OK, 1 on error.
Notes: (1) This finds the average color in a set of pixels that are roughly a distance from the c.c. boundary and in the background of the mask image.
NUMA* pixGetMomentByColumn | ( | PIX * | pix, |
l_int32 | order | ||
) |
Input: pix (1 bpp) order (of moment, either 1 or 2) Return: na of first moment of fg pixels, by column, or null on error
Input: pixd (<optional>; this can be null, equal to pixs, or different from pixs) pixs Return: pixd, or null on error
Notes: (1) This inverts pixs, for all pixel depths. (2) There are 3 cases: (a) pixd == null, ~src --> new pixd (b) pixd == pixs, ~src --> src (in-place) (c) pixd != pixs, ~src --> input pixd (3) For clarity, if the case is known, use these patterns: (a) pixd = pixInvert(NULL, pixs); (b) pixInvert(pixs, pixs); (c) pixInvert(pixd, pixs);
PIX* pixMakeAlphaFromMask | ( | PIX * | pixs, |
l_int32 | dist, | ||
BOX ** | pbox | ||
) |
Input: pixs (1 bpp) dist (blending distance; typically 10 - 30) &box (<optional return>="">, use null to get the full size Return: pixd (8 bpp gray), or null on error
Notes: (1) This generates a 8 bpp alpha layer that is opaque (256) over the FG of pixs, and goes transparent linearly away from the FG pixels, decaying to 0 (transparent) is an 8-connected distance given by . If == 0, this does a simple conversion from 1 to 8 bpp. (2) If &box == NULL, this returns an alpha mask that is the full size of pixs. Otherwise, the returned mask pixd covers just the FG pixels of pixs, expanded by in each direction (if possible), and the returned box gives the location of the returned mask relative to pixs. (3) This is useful for painting through a mask and allowing blending of the painted image with an underlying image in the mask background for pixels near foreground mask pixels. For example, with an underlying rgb image pix1, an overlaying image rgb pix2, binary mask pixm, and dist > 0, this blending is achieved with: pix3 = pixMakeAlphaFromMask(pixm, dist, &box); boxGetGeometry(box, &x, &y, NULL, NULL); pix4 = pixBlendWithGrayMask(pix1, pix2, pix3, x, y);
PIX* pixMakeMaskFromLUT | ( | PIX * | pixs, |
l_int32 * | tab | ||
) |
Input: pixs (2, 4 or 8 bpp; can be colormapped) tab (256-entry LUT; 1 means to write to mask) Return: pixd (1 bpp mask), or null on error
Notes: (1) This generates a 1 bpp mask image, where a 1 is written in the mask for each pixel in pixs that has a value corresponding to a 1 in the LUT. (2) The LUT should be of size 256.
PIX* pixMirroredTiling | ( | PIX * | pixs, |
l_int32 | w, | ||
l_int32 | h | ||
) |
Input: pixs (8 or 32 bpp, small tile; to be replicated) w, h (dimensions of output pix) Return: pixd (usually larger pix, mirror-tiled with pixs), or null on error
Notes: (1) This uses mirrored tiling, where each row alternates with LR flips and every column alternates with TB flips, such that the result is a tiling with identical 2 x 2 tiles, each of which is composed of these transforms: ----------------- | 1 | LR | ----------------- | TB | LR/TB | -----------------
Input: pixd (<optional>; this can be null, equal to pixs1, different from pixs1) pixs1 (can be == pixd) pixs2 (must be != pixd) Return: pixd always
Notes: (1) This gives the union of two images with equal depth, aligning them to the the UL corner. pixs1 and pixs2 need not have the same width and height. (2) There are 3 cases: (a) pixd == null, (src1 | src2) --> new pixd (b) pixd == pixs1, (src1 | src2) --> src1 (in-place) (c) pixd != pixs1, (src1 | src2) --> input pixd (3) For clarity, if the case is known, use these patterns: (a) pixd = pixOr(NULL, pixs1, pixs2); (b) pixOr(pixs1, pixs1, pixs2); (c) pixOr(pixd, pixs1, pixs2); (4) The size of the result is determined by pixs1. (5) The depths of pixs1 and pixs2 must be equal. (6) Note carefully that the order of pixs1 and pixs2 only matters for the in-place case. For in-place, you must have pixd == pixs1. Setting pixd == pixs2 gives an incorrect result: the copy puts pixs1 image data in pixs2, and the rasterop is then between pixs2 and pixs2 (a no-op).
l_int32 pixPaintSelfThroughMask | ( | PIX * | pixd, |
PIX * | pixm, | ||
l_int32 | x, | ||
l_int32 | y, | ||
l_int32 | searchdir, | ||
l_int32 | mindist, | ||
l_int32 | tilesize, | ||
l_int32 | ntiles, | ||
l_int32 | distblend | ||
) |
Input: pixd (8 bpp gray or 32 bpp rgb; not colormapped) pixm (1 bpp mask) x, y (origin of pixm relative to pixd; must not be negative) searchdir (L_HORIZ, L_VERT or L_BOTH_DIRECTIONS) mindist (min distance of nearest tile edge to box; >= 0) tilesize (requested size for tiling; may be reduced) ntiles (number of tiles tested in each row/column) distblend (distance outside the fg used for blending with pixs) Return: 0 if OK; 1 on error
Notes: (1) In-place operation; pixd is changed. (2) If pixm == NULL, it's a no-op. (3) The mask origin is placed at (x,y) on pixd, and the operation is clipped to the intersection of pixd and the fg of the mask. (4) is the the requested size for tiling. The actual actual size for each c.c. will be bounded by the minimum dimension of the c.c. (5) For , and , see pixFindRepCloseTile(). They determine the set of possible tiles that can be used to build a larger mirrored tile to paint onto pixd through the c.c. of pixm. (6) is used for alpha blending. It is only applied if there is exactly one c.c. in the mask. Use distblend == 0 to skip blending and just paint through the 1 bpp mask. (7) To apply blending to more than 1 component, call this function repeatedly with , and representing one component of the mask each time. This would be done as follows, for an underlying image pixs and mask pixm of components to fill: Boxa *boxa = pixConnComp(pixm, &pixa, 8); n = boxaGetCount(boxa); for (i = 0; i < n; i++) { Pix *pix = pixaGetPix(pixa, i, L_CLONE); Box *box = pixaGetBox(pixa, i, L_CLONE); boxGetGeometry(box, &bx, &by, &bw, &bh); pixPaintSelfThroughMask(pixs, pix, bx, by, searchdir, mindist, tilesize, ntiles, distblend); pixDestroy(&pix); boxDestroy(&box); } pixaDestroy(&pixa); boxaDestroy(&boxa); (8) If no tiles can be found, this falls back to estimating the color near the boundary of the region to be textured. (9) This can be used to replace the pixels in some regions of an image by selected neighboring pixels. The mask represents the pixels to be replaced. For each connected component in the mask, this function selects up to two tiles of neighboring pixels to be used for replacement of pixels represented by the component (i.e., under the FG of that component in the mask). After selection, mirror replication is used to generate an image that is large enough to cover the component. Alpha blending can also be used outside of the component, but near the edge, to blur the transition between painted and original pixels.
Input: pixd (1, 2, 4, 8, 16 or 32 bpp; or colormapped) pixm (<optional> 1 bpp mask) x, y (origin of pixm relative to pixd; can be negative) val (pixel value to set at each masked pixel) Return: 0 if OK; 1 on error
Notes: (1) In-place operation. Calls pixSetMaskedCmap() for colormapped images. (2) For 1, 2, 4, 8 and 16 bpp gray, we take the appropriate number of least significant bits of val. (3) If pixm == NULL, it's a no-op. (4) The mask origin is placed at (x,y) on pixd, and the operation is clipped to the intersection of rectangles. (5) For rgb, the components in val are in the canonical locations, with red in location COLOR_RED, etc. (6) Implementation detail 1: For painting with val == 0 or val == maxval, you can use rasterop. If val == 0, invert the mask so that it's 0 over the region into which you want to write, and use PIX_SRC & PIX_DST to clear those pixels. To write with val = maxval (all 1's), use PIX_SRC | PIX_DST to set all bits under the mask. (7) Implementation detail 2: The rasterop trick can be used for depth > 1 as well. For val == 0, generate the mask for depth d from the binary mask using pixmd = pixUnpackBinary(pixm, d, 1); and use pixRasterop() with PIX_MASK. For val == maxval, pixmd = pixUnpackBinary(pixm, d, 0); and use pixRasterop() with PIX_PAINT. But note that if d == 32 bpp, it is about 3x faster to use the general implementation (not pixRasterop()). (8) Implementation detail 3: It might be expected that the switch in the inner loop will cause large branching delays and should be avoided. This is not the case, because the entrance is always the same and the compiler can correctly predict the jump.
l_int32 pixSetMasked | ( | PIX * | pixd, |
PIX * | pixm, | ||
l_uint32 | val | ||
) |
Input: pixd (1, 2, 4, 8, 16 or 32 bpp; or colormapped) pixm (<optional> 1 bpp mask; no operation if NULL) val (value to set at each masked pixel) Return: 0 if OK; 1 on error
Notes: (1) In-place operation. (2) NOTE: For cmapped images, this calls pixSetMaskedCmap(). must be the 32-bit color representation of the RGB pixel. It is not the index into the colormap! (2) If pixm == NULL, a warning is given. (3) This is an implicitly aligned operation, where the UL corners of pixd and pixm coincide. A warning is issued if the two image sizes differ significantly, but the operation proceeds. (4) Each pixel in pixd that co-locates with an ON pixel in pixm is set to the specified input value. Other pixels in pixd are not changed. (5) You can visualize this as painting the color through the mask, as a stencil. (6) If you do not want to have the UL corners aligned, use the function pixSetMaskedGeneral(), which requires you to input the UL corner of pixm relative to pixd. (7) Implementation details: see comments in pixPaintThroughMask() for when we use rasterop to do the painting.
Input: pixd (8, 16 or 32 bpp) pixm (<optional> 1 bpp mask; no operation if null) val (value to set at each masked pixel) x, y (location of UL corner of pixm relative to pixd; can be negative) Return: 0 if OK; 1 on error
Notes: (1) This is an in-place operation. (2) Alignment is explicit. If you want the UL corners of the two images to be aligned, use pixSetMasked(). (3) A typical use would be painting through the foreground of a small binary mask pixm, located somewhere on a larger pixd. Other pixels in pixd are not changed. (4) You can visualize this as painting the color through the mask, as a stencil. (5) This uses rasterop to handle clipping and different depths of pixd. (6) If pixd has a colormap, you should call pixPaintThroughMask(). (7) Why is this function here, if pixPaintThroughMask() does the same thing, and does it more generally? I've retained it here to show how one can paint through a mask using only full image rasterops, rather than pixel peeking in pixm and poking in pixd. It's somewhat baroque, but I found it amusing.
PIX* pixSetUnderTransparency | ( | PIX * | pixs, |
l_uint32 | val, | ||
l_int32 | debug | ||
) |
Input: pixs (32 bpp rgba) val (32 bit unsigned color to use where alpha == 0) debug (displays layers of pixs) Return: pixd (32 bpp rgba), or null on error
Notes: (1) This sets the r, g and b components under every fully transparent alpha component to . The alpha components are unchanged. (2) Full transparency is denoted by alpha == 0. Setting all pixels to a constant where alpha is transparent can improve compressibility by reducing the entropy. (3) The visual result depends on how the image is displayed. (a) For display devices that respect the use of the alpha layer, this will not affect the appearance. (b) For typical leptonica operations, alpha is ignored, so there will be a change in appearance because this resets the rgb values in the fully transparent region. (4) pixRead() and pixWrite() will, by default, read and write 4-component (rgba) pix in png format. To ignore the alpha component after reading, or omit it on writing, pixSetSpp(..., 3). (5) Here are some examples: * To convert all fully transparent pixels in a 4 component (rgba) png file to white: pixs = pixRead(<infile>); pixd = pixSetUnderTransparency(pixs, 0xffffff00, 0); * To write pixd with the alpha component: pixWrite(<outfile>, pixd, IFF_PNG); * To write and rgba image without the alpha component, first do: pixSetSpp(pixd, 3); If you later want to use the alpha, spp must be reset to 4. * (fancier) To remove the alpha by blending the image over a white background: pixRemoveAlpha() This changes all pixel values where the alpha component is not opaque (255). (6) Caution. rgb images in leptonica typically have value 0 in the alpha channel, which is fully transparent. If spp for such an image were changed from 3 to 4, the image becomes fully transparent, and this function will set each pixel to . If you really want to set every pixel to the same value, use pixSetAllArbitrary(). (7) This is useful for compressing an RGBA image where the part of the image that is fully transparent is random junk; compression is typically improved by setting that region to a constant. For rendering as a 3 component RGB image over a uniform background of arbitrary color, use pixAlphaBlendUniform().
PIX* pixSubtract | ( | PIX * | pixd, |
PIX * | pixs1, | ||
PIX * | pixs2 | ||
) |
Input: pixd (<optional>; this can be null, equal to pixs1, equal to pixs2, or different from both pixs1 and pixs2) pixs1 (can be == pixd) pixs2 (can be == pixd) Return: pixd always
Notes: (1) This gives the set subtraction of two images with equal depth, aligning them to the the UL corner. pixs1 and pixs2 need not have the same width and height. (2) Source pixs2 is always subtracted from source pixs1. The result is pixs1 \ pixs2 = pixs1 & (~pixs2) (3) There are 4 cases: (a) pixd == null, (src1 - src2) --> new pixd (b) pixd == pixs1, (src1 - src2) --> src1 (in-place) (c) pixd == pixs2, (src1 - src2) --> src2 (in-place) (d) pixd != pixs1 && pixd != pixs2), (src1 - src2) --> input pixd (4) For clarity, if the case is known, use these patterns: (a) pixd = pixSubtract(NULL, pixs1, pixs2); (b) pixSubtract(pixs1, pixs1, pixs2); (c) pixSubtract(pixs2, pixs1, pixs2); (d) pixSubtract(pixd, pixs1, pixs2); (5) The size of the result is determined by pixs1. (6) The depths of pixs1 and pixs2 must be equal.
Input: pix (1 bpp) threshold &above (<return> 1 if above threshold; 0 if equal to or less than threshold) tab8 (<optional> 8-bit pixel lookup table) Return: 0 if OK; 1 on error
Notes: (1) This sums the ON pixels and returns immediately if the count goes above threshold. It is therefore more efficient for matching images (by running this function on the xor of the 2 images) than using pixCountPixels(), which counts all pixels before returning.
NUMA* pixVarianceByColumn | ( | PIX * | pix, |
BOX * | box | ||
) |
Input: pix (8 or 16 bpp; no colormap) box (<optional> clipping box for variance; can be null) Return: na of rmsdev by column, or null on error
Notes: (1) To resample for a bin size different from 1, use numaUniformSampling() on the result of this function. (2) We are actually computing the RMS deviation in each row. This is the square root of the variance.
NUMA* pixVarianceByRow | ( | PIX * | pix, |
BOX * | box | ||
) |
Input: pix (8 or 16 bpp; no colormap) box (<optional> clipping box for variance; can be null) Return: na of rmsdev by row, or null on error
Notes: (1) To resample for a bin size different from 1, use numaUniformSampling() on the result of this function. (2) We are actually computing the RMS deviation in each row. This is the square root of the variance.
l_int32 pixVarianceInRect | ( | PIX * | pix, |
BOX * | box, | ||
l_float32 * | prootvar | ||
) |
Input: pix (1, 2, 4, 8 bpp; not cmapped) box (<optional> if null, use entire image) &rootvar (<return> sqrt variance of pixel values in region) Return: 0 if OK; 1 on error
Input: pixd (<optional>; this can be null, equal to pixs1, different from pixs1) pixs1 (can be == pixd) pixs2 (must be != pixd) Return: pixd always
Notes: (1) This gives the XOR of two images with equal depth, aligning them to the the UL corner. pixs1 and pixs2 need not have the same width and height. (2) There are 3 cases: (a) pixd == null, (src1 ^ src2) --> new pixd (b) pixd == pixs1, (src1 ^ src2) --> src1 (in-place) (c) pixd != pixs1, (src1 ^ src2) --> input pixd (3) For clarity, if the case is known, use these patterns: (a) pixd = pixXor(NULL, pixs1, pixs2); (b) pixXor(pixs1, pixs1, pixs2); (c) pixXor(pixd, pixs1, pixs2); (4) The size of the result is determined by pixs1. (5) The depths of pixs1 and pixs2 must be equal. (6) Note carefully that the order of pixs1 and pixs2 only matters for the in-place case. For in-place, you must have pixd == pixs1. Setting pixd == pixs2 gives an incorrect result: the copy puts pixs1 image data in pixs2, and the rasterop is then between pixs2 and pixs2 (a no-op).
Input: pix (all depths; colormap OK) &empty (<return> 1 if all bits in image data field are 0; 0 otherwise) Return: 0 if OK; 1 on error
Notes: (1) For a binary image, if there are no fg (black) pixels, empty = 1. (2) For a grayscale image, if all pixels are black (0), empty = 1. (3) For an RGB image, if all 4 components in every pixel is 0, empty = 1. (4) For a colormapped image, pixel values are 0. The colormap is ignored.