1vpSetImage(3) Library Functions Manual vpSetImage(3)
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6 vpSetImage - specify an image array
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9 #include <volpack.h>
10 vpResult
12 vpSetImage(vpc, image, width, height, scan_bytes, pixel_type)
13 vpContext *vpc;
14 unsigned char *image;
15 int width, height;
16 int scan_bytes;
17 int pixel_type;
18
20 vpc VolPack context from vpCreateContext.
21 image 2D array for storing result images.
23 width Width of image in pixels.
25 height Height of image in pixels.
27 scan_bytes
29 Number of bytes per scanline in image array.
30 pixel_type
32 Code indicating the format of each pixel in the array.
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35 vpSetImage is used to specify a buffer for storing the result image
36 during rendering. The width and height parameters specify the size of
37 the result image. The clipping window (see vpWindow(3) or vpWindow‐
38 PHIGS(3)) is scaled to exactly match the specified size. The
39 scan_bytes argument specifies the size of a scanline in the image
40 array, in bytes. This argument can be used to add padding to the end
41 of each scanline to satisfy alignment restrictions (e.g. raster opera‐
42 tions sometimes require the beginning of each scanline to lie on a word
43 boundary). The pixel_type argument specifies the format of a pixel.
44 The following formats are supported:
45 VP_ALPHA
47 Each pixel is one byte and contains an 8-bit alpha channel (con‐
48 taining an opacity or coverage value for the pixel).
49 VP_LUMINANCE
51 Each pixel is one byte and contains an 8-bit grayscale inten‐
52 sity.
53 VP_LUMINANCEA
55 Each pixel is two bytes and contains an 8-bit grayscale inten‐
56 sity followed by an 8-bit alpha channel.
57 VP_RGB Each pixel is three bytes and contains an RGB color (8
59 bits/channel). The R channel is stored first, followed by G and
60 then B.
61 VP_RGBA
63 Each pixel is four bytes and contains an RGBA color with an
64 alpha channel (8 bits/channel). The R channel is stored first,
65 followed by G, B and A.
66 VP_BGR Each pixel is three bytes and contains an RGB color (8
68 bits/channel). The B channel is stored first, follow by G and
69 then R.
70 VP_ABGR
72 Each pixel is four bytes and contains an RGBA color with an
73 alpha channel (8 bits/channel). The A channel is stored first,
74 followed by B, G and R.
75 The formats VP_LUMINANCE and VP_LUMINANCEA may only be used with
77 grayscale shaders (the color_channels argument to vpSetLookupShader
78 must be 1, or if you are using a callback function for shading you must
79 use the VP_GRAY_SHADE_FUNC argument to vpSetCallback). The formats
80 VP_RGB, VP_RGBA, VP_BGR and VP_ABGR may only be used with color
81 shaders. The format VP_ALPHA may be used with either type of shader.
82 The size of the image array must be: unsigned char
84 image[height][scan_bytes]; The scan_bytes argument must be at least
85 width times the number of bytes per pixel. Pixels in a horizontal
86 scanline are packed next to each other, regardless of the size of the
87 pixel. Any extra padding bytes at the end of a scanline are not modi‐
88 fied.
89 The alpha channel may be used to composite the rendered image against a
91 background image. Alpha gives the fraction of the background that is
92 visible through the rendered image (0 for fully visible, 255 for fully
93 obscured). As an example, to change the background color of the image
94 to a solid color C, modify the color of each pixel in the image accord‐
95 ing to the formula: color(x,y) += C * (1 - alpha(x,y)/255)
96
98 The current image array properties can be retrieved with the following
99 state variable codes (see vpGeti(3)): VP_IMAGE, VP_IMAGE_WIDTH,
100 VP_IMAGE_HEIGHT, VP_IMAGE_SCAN_SIZE, VP_PIXEL_TYPE.
101
103 The return value is always VP_OK.
104
106 VolPack(3), vpCreateContext(3), vpRenderRawVolume(3)
107VolPack vpSetImage(3)