1mlib_ImageSubsampleBinaryTomGerdaiya(L3iMbLILBi)brarmyliFbu_nIcmtaigoenSsubsampleBinaryToGray(3MLIB)
2
6 mlib_ImageSubsampleBinaryToGray - subsamples a binary image and con‐
7 verts it to a grayscale image
8
10 cc [ flag... ] file... -lmlib [ library... ]
11 #include <mlib.h>
12 mlib_status mlib_ImageSubsampleBinaryToGray(mlib_image *dst,
14 const mlib_image *src, mlib_d64 xscale, mlib_d64 yscale,
15 const mlib_u8 *lutGray);
16
19 The mlib_ImageSubsampleBinaryToGray() function subsamples a binary
20 (MLIB_BIT) image and converts it to a grayscale (MLIB_BYTE) image.
21 The subsampling algorithm performs the scaling operation by accumulat‐
24 ing all the bits in the source image that correspond to the destination
25 pixel and, based on the x and y scaling factors, reserving consecutive
26 indexes in the colormap for the maximum number of gray levels possible
27 in the destination image. The destination image pixel values of this
28 function are either gray levels or indexes (if lutGray==NULL).
29 For representing the source block of pixels that is used to determine
32 destination pixel values, the index 0 represents a block with no 1's
33 (all 0's), the index 1 represents a block with a single 1, and so on.
34 If the scaling factors require a fractional block of source pixels to
35 determine a destination pixel value, the block size is rounded up. For
36 example, if a 2.2-by-2.2 block of source pixels would be required to
37 determine destination pixel values, a 3-by-3 block is used, resulting
38 in 10 possible gray levels and therefore 10 colormap indexes, whose
39 values are 0 through 9.
40 The width and height of the source block for a destination pixel are
43 computed as:
44 blockX = (int)ceil(1.0/xscale);
46 blockY = (int)ceil(1.0/yscale);
47 If we denote a pixel's location in an image by its column number and
51 row number (both counted from 0), the destination pixel at (i, j) is
52 backward mapped to the source block whose upper-left corner pixel is at
53 (xValues[i], yValues[j]), where
54 xValues[i] = (int)(i/xscale + 0.5);
56 yValues[j] = (int)(j/yscale + 0.5);
57 The width and height of the filled area in the destination are
61 restricted by
62 dstW = (int)(srcWidth * xscale);
64 dstH = (int)(srcHeight * yscale);
65 where srcWidth and srcHeight are width and height of the source image.
69 Since the block size in source is defined from scale factors with
72 roundup, some blocks (the rightmost and the bottommost blocks) may
73 overrun the border of the source image by 1 pixel. In this case, such
74 blocks are moved by 1 pixel to left/up direction in order to be inside
75 of the source image.
76
78 The function takes the following arguments:
79 dst Pointer to destination image . It must be of type MLIB_BYTE
81 and have just one channel.
82 src Pointer to source image. It must be of type MLIB_BIT and
85 have just one channel.
86 xscale X scale factor. 0.0 < xscale ≤ 1.0.
89 yscale Y scale factor. 0.0 < yscale ≤ 1.0.
92 lutGray Pointer to a grayscale lookup-table.
95
98 The function returns MLIB_SUCCESS if successful. Otherwise it returns
99 MLIB_FAILURE.
100
102 See attributes(5) for descriptions of the following attributes:
103 ┌─────────────────────────────┬─────────────────────────────┐
108 │ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
109 ├─────────────────────────────┼─────────────────────────────┤
110 │Interface Stability │Committed │
111 ├─────────────────────────────┼─────────────────────────────┤
112 │MT-Level │MT-Safe │
113 └─────────────────────────────┴─────────────────────────────┘
114
116 mlib_ImageZoomTranslateToGray(3MLIB), mlib_ImageSubsampleAver‐
117 age(3MLIB), attributes(5)
118SunOS 5.11 2 Mar 2m0l0i7b_ImageSubsampleBinaryToGray(3MLIB)