mlib_ImageColorDitherFree(3MLIB) mediaLib Library Functions mlib_ImageColorDitherFree(3MLIB)NAME
mlib_ImageColorDitherFree - release the internal data structure for image dithering
SYNOPSIS
cc [ flag... ] file... -lmlib [ library... ]
#include <mlib.h>
void mlib_ImageColorDitherFree(void *colormap);
DESCRIPTION
The mlib_ImageColorDitherFree() function releases an internal data structure, colormap, which was created by mlib_ImageColorDitherInit()
and was used by one of the following functions for image dithering:
mlib_ImageColorErrorDiffusion3x3
mlib_ImageColorErrorDiffusionMxN
mlib_ImageColorOrderedDither8x8
mlib_ImageColorOrderedDitherMxN
PARAMETERS
The function takes the following arguments:
colormap Internal data structure for image dithering.
RETURN VALUES
None.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Interface Stability |Evolving |
+-----------------------------+-----------------------------+
|MT-Level |MT-Safe |
+-----------------------------+-----------------------------+
SEE ALSO mlib_ImageColorDitherInit(3MLIB), mlib_ImageColorErrorDiffusion3x3(3MLIB), mlib_ImageColorErrorDiffusionMxN(3MLIB), mlib_ImageColorOrdered-
Dither8x8(3MLIB), mlib_ImageColorOrderedDitherMxN(3MLIB), attributes(5)SunOS 5.10 10 Nov 2004 mlib_ImageColorDitherFree(3MLIB)
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mlib_ImageColorDitherInit(3MLIB) mediaLib Library Functions mlib_ImageColorDitherInit(3MLIB)NAME
mlib_ImageColorDitherInit - initialization for image dithering
SYNOPSIS
cc [ flag... ] file... -lmlib [ library... ]
#include <mlib.h>
mlib_status mlib_ImageColorDitherInit(void **colormap, const mlib_s32 *dimensions, mlib_type intype, mlib_type outtype, mlib_s32 channels,
mlib_s32 entries, mlib_s32 offset, void **lut);
DESCRIPTION
The mlib_ImageColorDitherInit() function creates an internal data structure, colormap, which can be used by one of the following functions
for image dithering:
mlib_ImageColorErrorDiffusion3x3
mlib_ImageColorErrorDiffusionMxN
mlib_ImageColorOrderedDither8x8
mlib_ImageColorOrderedDitherMxN
The lut might have either 1 or 3 channels. The type of the lut can be one of the following:
MLIB_BYTE in, MLIB_BYTE out (i.e., BYTE-to-BYTE)
MLIB_BIT in, MLIB_BYTE out (i.e., BIT-to-BYTE)
If dimensions == NULL, then no colorcube will be created. In this case, the user-provided lookup table, lut, will be used for dithering.
If dimensions != NULL, then a colorcube is created from scratch in a way shown in the following example.
To dither an RGB image of type MLIB_BYTE to a color-indexed image of type MLIB_BYTE, we can use the following parameters:
mlib_s32 dimensions[] = {2, 3, 4};
mlib_type intype = MLIB_BYTE;
mlib_type outtype = MLIB_BYTE;
mlib_s32 channels = 3;
mlib_s32 offset = 6;
These values would lead to the creation of a colorcube that would dither red values in the source image to one of 2 red levels, green val-
ues to one of 3 green levels, and blue values to one of 4 blue levels. You could picture this colorcube as a cube with dimensions of 2, 3,
and 4. The index values assigned to the elements in that cube can be described by the following lookup table:
Indexes Red Values Green Values Blue Values
0
...
5
6 0 0 0
7 255 0 0
8 0 128 0
9 255 128 0
10 0 255 0
11 255 255 0
12 0 0 85
13 255 0 85
14 0 128 85
15 255 128 85
16 0 255 85
17 255 255 85
18 0 0 170
19 255 0 170
20 0 128 170
21 255 128 170
22 0 255 170
23 255 255 170
24 0 0 255
25 255 0 255
26 0 128 255
27 255 128 255
28 0 255 255
29 255 255 255
...
The distance between level changes in each channel of the lookup table is determined by the following formulas:
multipliers[0] = signof(dimensions[0])*1;
multipliers[i] = signof(dimensions[i])*
abs(multipliers[i-1]*dimension[i-1]);
A negative dimensions[i], so as to a negative multipliers[i], indicates that the values in a color ramp for channel i should appear in
decreasing as opposed to increasing order.
For each channel i, the values of the levels are determined by the following formulas:
double delta = (dataMax - dataMin)/(abs(dimensions[i]) - 1);
int levels[j] = (int)(j*delta + 0.5);
where dataMax and dataMin are the maximum and minimum values, respectively, for data type intype.
Whenever a colorcube is created, if lut != NULL, the lookup table will be filled according to the colorcube and supplied parameters like
offset. For the example shown above, the lookup table will start from line 6. In this case, it is the user's responsibility to allocate
memory for the lookup table.
PARAMETERS
The function takes the following arguments:
colormap Internal data structure for image dithering.
dimensions Dimensions of the colorcube in the colormap structure.
intype Data type of the source image and the lookup table.
outtype Data type of the destination indexed image.
channels Number of channels of the lookup table and source image.
entries Number of entries of the lookup table.
offset Index offset of the lookup table.
lut Lookup table.
RETURN VALUES
The function returns MLIB_SUCCESS if successful. Otherwise it returns MLIB_FAILURE.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Interface Stability |Evolving |
+-----------------------------+-----------------------------+
|MT-Level |MT-Safe |
+-----------------------------+-----------------------------+
SEE ALSO mlib_ImageColorDitherFree(3MLIB), mlib_ImageColorErrorDiffusion3x3(3MLIB), mlib_ImageColorErrorDiffusionMxN(3MLIB), mlib_ImageColorOrdered-
Dither8x8(3MLIB), mlib_ImageColorOrderedDitherMxN(3MLIB), attributes(5)SunOS 5.10 10 Nov 2004 mlib_ImageColorDitherInit(3MLIB)