- Создано системой
1.8.15
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Leptonica
1.54
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Классы | |
| struct | L_Box3d |
Макросы | |
| #define | DEBUG_MC_COLORS 0 |
| #define | DEBUG_SPLIT_AXES 0 |
Определения типов | |
| typedef struct L_Box3d | L_BOX3D |
Переменные | |
| static const l_int32 | DEFAULT_SIG_BITS = 5 |
| static const l_int32 | MAX_ITERS_ALLOWED = 5000 |
| static const l_float32 | FRACT_BY_POPULATION = 0.85 |
| static const l_int32 | DIF_CAP = 100 |
| #define DEBUG_MC_COLORS 0 |
| #define DEBUG_SPLIT_AXES 0 |
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Input: pixel (32 bit rgb)
rshift (of component: 8 - sigbits)
mask (over sigbits)
sigbits
&index (<return> rgb index value)
Return: void
Notes: (1) This is used on each pixel in the source image. No checking is done on input values.
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Input: histo (array; in rgb colorspace)
sigbits
vbox (input 3D box)
&vbox1, vbox2 (<return> vbox split in two parts)
Return: 0 if OK, 1 on error
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Input: pixs (32 bpp; rgb color)
depth (of colormap)
histo
histosize
sigbits
Return: colormap, or null on error
Notes: (1) This is used when the number of colors in the histo is not greater than maxcolors. (2) As a side-effect, the histo becomes an inverse colormap, labeling the cmap indices for each existing color.
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pixcmapGenerateFromMedianCuts()
Input: lh (priority queue of pointers to vboxes)
histo
sigbits (valid: 5 or 6)
Return: cmap, or null on error
Notes: (1) Each vbox in the heap represents a color in the colormap. (2) As a side-effect, the histo becomes an inverse colormap, where the part of the array correpsonding to each vbox is labeled with the cmap index for that vbox. Then for each rgb pixel, the colormap index is found directly by mapping the rgb value to the histo array index.
| PIX* pixFewColorsMedianCutQuantMixed | ( | PIX * | pixs, |
| l_int32 | ncolor, | ||
| l_int32 | ngray, | ||
| l_int32 | maxncolors, | ||
| l_int32 | darkthresh, | ||
| l_int32 | lightthresh, | ||
| l_int32 | diffthresh | ||
| ) |
pixFewColorsMedianCutQuantMixed()
Input: pixs (32 bpp rgb)
ncolor (number of colors to be assigned to pixels with
significant color)
ngray (number of gray colors to be used; must be >= 2)
maxncolors (maximum number of colors to be returned
from pixColorsForQuantization(); use 0 for default)
darkthresh (threshold near black; if the lightest component
is below this, the pixel is not considered to
be gray or color; use 0 for default)
lightthresh (threshold near white; if the darkest component
is above this, the pixel is not considered to
be gray or color; use 0 for default)
diffthresh (thresh for the max difference between component
values; for differences below this, the pixel
is considered to be gray; use 0 for default)
considered gray; use 0 for default)
Return: pixd (8 bpp, median cut quantized for pixels that are
not gray; gray pixels are quantized separately
over the full gray range); null if too many colors
or on error
Notes: (1) This is the "few colors" version of pixMedianCutQuantMixed(). It fails (returns NULL) if it finds more than maxncolors, but otherwise it gives the same result. (2) Recommended input parameters are: @maxncolors: 20 @darkthresh: 20 @lightthresh: 244 @diffthresh: 15 (any higher can miss colors differing slightly from gray) (3) Both ncolor and ngray should be at least equal to maxncolors. If they're not, they are automatically increased, and a warning is given. (4) If very little color content is found, the input is converted to gray and quantized in equal intervals. (5) This can be useful for quantizing orthographically generated images such as color maps, where there may be more than 256 colors because of aliasing or jpeg artifacts on text or lines, but there are a relatively small number of solid colors. (6) Example of usage: // Try to quantize, using default values for mixed med cut Pix *pixq = pixFewColorsMedianCutQuantMixed(pixs, 100, 20, 0, 0, 0, 0); if (!pixq) // too many colors; don't quantize pixq = pixClone(pixs);
Input: pixs (32 bpp; rgb color)
sigbits (valid: 5, 6)
subsample (integer > 0)
Return: vbox (minimum 3D box in color space enclosing all pixels),
or null on error
Notes: (1) Computes the minimum 3D box in color space enclosing all pixels in the image.
Input: pixs (32 bpp; rgb color)
sigbits (valid: 5 or 6)
subsample (integer > 0)
Return: histo (1-d array, giving the number of pixels in
each quantized region of color space), or null on error
Notes: (1) Array is indexed by (3 * sigbits) bits. The array size is 2^(3 * sigbits). (2) Indexing into the array from rgb uses red sigbits as most significant and blue as least.
Input: pixs (32 bpp; rgb color)
ditherflag (1 for dither; 0 for no dither)
Return: pixd (8 bit with colormap), or null on error
Notes: (1) Simple interface. See pixMedianCutQuantGeneral() for use of defaulted parameters.
| PIX* pixMedianCutQuantGeneral | ( | PIX * | pixs, |
| l_int32 | ditherflag, | ||
| l_int32 | outdepth, | ||
| l_int32 | maxcolors, | ||
| l_int32 | sigbits, | ||
| l_int32 | maxsub, | ||
| l_int32 | checkbw | ||
| ) |
Input: pixs (32 bpp; rgb color)
ditherflag (1 for dither; 0 for no dither)
outdepth (output depth; valid: 0, 1, 2, 4, 8)
maxcolors (between 2 and 256)
sigbits (valid: 5 or 6; use 0 for default)
maxsub (max subsampling, integer; use 0 for default;
1 for no subsampling)
checkbw (1 to check if color content is very small,
0 to assume there is sufficient color)
Return: pixd (8 bit with colormap), or null on error
Notes: (1) @maxcolors must be in the range [2 ... 256]. (2) Use @outdepth = 0 to have the output depth computed as the minimum required to hold the actual colors found, given the @maxcolors constraint. (3) Use @outdepth = 1, 2, 4 or 8 to specify the output depth. In that case, @maxcolors must not exceed 2^(outdepth). (4) If there are fewer quantized colors in the image than @maxcolors, the colormap is simply generated from those colors. (5) @maxsub is the maximum allowed subsampling to be used in the computation of the color histogram and region of occupied color space. The subsampling is chosen internally for efficiency, based on the image size, but this parameter limits it. Use @maxsub = 0 for the internal default, which is the maximum allowed subsampling. Use @maxsub = 1 to prevent subsampling. In general use @maxsub >= 1 to specify the maximum subsampling to be allowed, where the actual subsampling will be the minimum of this value and the internally determined default value. (6) If the image appears gray because either most of the pixels are gray or most of the pixels are essentially black or white, the image is trivially quantized with a grayscale colormap. The reason is that median cut divides the color space into rectangular regions, and it does a very poor job if all the pixels are near the diagonal of the color space cube.
| PIX* pixMedianCutQuantMixed | ( | PIX * | pixs, |
| l_int32 | ncolor, | ||
| l_int32 | ngray, | ||
| l_int32 | darkthresh, | ||
| l_int32 | lightthresh, | ||
| l_int32 | diffthresh | ||
| ) |
Input: pixs (32 bpp; rgb color)
ncolor (maximum number of colors assigned to pixels with
significant color)
ngray (number of gray colors to be used; must be >= 2)
darkthresh (threshold near black; if the lightest component
is below this, the pixel is not considered to
be gray or color; uses 0 for default)
lightthresh (threshold near white; if the darkest component
is above this, the pixel is not considered to
be gray or color; use 0 for default)
diffthresh (thresh for the max difference between component
values; for differences below this, the pixel
is considered to be gray; use 0 for default)
Return: pixd (8 bpp cmapped), or null on error
Notes: (1) ncolor + ngray must not exceed 255. (2) The method makes use of pixMedianCutQuantGeneral() with minimal addition. (a) Preprocess the image, setting all pixels with little color to black, and populating an auxiliary 8 bpp image with the expected colormap values corresponding to the set of quantized gray values. (b) Color quantize the altered input image to n + 1 colors. (c) Augment the colormap with the gray indices, and substitute the gray quantized values from the auxiliary image for those in the color quantized output that had been quantized as black. (3) Median cut color quantization is relatively poor for grayscale images with many colors, when compared to octcube quantization. Thus, for images with both gray and color, it is important to quantize the gray pixels by another method. Here, we are conservative in detecting color, preferring to use a few extra bits to encode colorful pixels that push them to gray. This is particularly reasonable with this function, because it handles the gray and color pixels separately, using median cut color quantization for the color pixels and equal-bin grayscale quantization for the non-color pixels.
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Input: pixs (32 bpp; rgb color)
ditherflag (1 for dither; 0 for no dither)
outdepth
cmap
indexmap
histosize
sigbits
Return: pixd (quantized to colormap), or null on error
Notes: (1) The indexmap is a LUT that takes the rgb indices of the pixel and returns the index into the colormap. (2) If ditherflag is 1, @outdepth is ignored and the output depth is set to 8.
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Input: vbox (3d region of color space for one quantized color)
histo
sigbits (valid: 5 or 6)
index (if >= 0, assign to all colors in histo in this vbox)
&rval, &gval, &bval (<returned> average color)
Return: cmap, or null on error
Notes: (1) The vbox represents one color in the colormap. (2) If index >= 0, as a side-effect, all array elements in the histo corresponding to the vbox are labeled with this cmap index for that vbox. Otherwise, the histo array is not changed. (3) The vbox is quantized in sigbits. So the actual 8-bit color components are found by multiplying the quantized value by either 4 or 8. We must add 0.5 to the quantized index before multiplying to get the approximate 8-bit color in the center of the vbox; otherwise we get values on the lower corner.
Input: vbox (3d region of color space for one quantized color)
histo
sigbits (valid: 5 or 6)
Return: number of image pixels in this region, or 0 on error
Input: vbox (3d region of color space for one quantized color) Return: quantized volume of vbox, or 0 on error
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1.8.15