mlib_ImageZoomTranslateBlend(3mlib)

1mlib_ImageZoomTranslateBlenmde(d3iMaLLIiBb)Library Fmulnicbt_iIomnasgeZoomTranslateBlend(3MLIB)
2
3
4

NAME

6       mlib_ImageZoomTranslateBlend - image scaling with alpha blending
7

SYNOPSIS

9       cc [ flag... ] file... -lmlib [ library... ]
10       #include <mlib.h>
11
12       mlib_status mlib_ImageZoomTranslateBlend(mlib_image *dst,
13            const mlib_image *src, mlib_d64 zoomx, mlib_d64 zoomy,
14            mlib_d64 tx, mlib_d64 ty, mlib_filter filter, mlib_edge edge,
15            mlib_blend blend, mlib_s32 alpha, mlib_s32 cmask);
16
17

DESCRIPTION

19       The  mlib_ImageZoomTranslateBlend() function will enlarge or minify the
20       source image by the X and Y zoom factors, with translation,  and  blend
21       it with the destination image.
22
23
24       It uses the following equation for coordinate mapping:
25
26         xd = zoomx*xs + tx
27         yd = zoomy*ys + ty
28
29
30
31       where  a  point with coordinates (xs, ys) in the source image is mapped
32       to a point with coordinates (xd, yd) in the destination image.
33
34
35       The center of the upper-left corner pixel of an  image  is  located  at
36       (0.5, 0.5).
37
38
39       The  alpha  blending  is  closely  combined  with  the interpolation to
40       achieve better performance.  Part of alpha blending has to be performed
41       before  or  together  with the interpolation if the source image has an
42       alpha channel. In that case, the color components of  each  neighboring
43       source  pixel  which participates in the interpolation (src_r and etc.)
44       have to be pre-multiplied by the alpha component  of  the  same  source
45       pixel (src_a).  After the interpolation, the overall alpha (alpha), the
46       interpolated source alpha (interp_a) and the destination pixel's origi‐
47       nal  alpha  (dst_a,  if  any) are used to blend the interpolated source
48       pixel (with components interp_r and etc.) with  the  destination  pixel
49       (with components dst_r and etc.).
50
51
52       The  MLIB_BLEND_GTK_SRC  blending  is  similar  to  the SRC rule of the
53       Porter-Duff rules for image compositing. It is defined by
54
55         Cd = Cs
56         Ad = As
57
58
59
60       in general, and by the following formula for this function:
61
62         if (interp_a != 0.0) {
63              if (dst_has_alpha) {
64                   dst_r = interp_r/interp_a;
65                   dst_g = interp_g/interp_a;
66                   dst_b = interp_b/interp_a;
67                   dst_a = interp_a;
68              } else {
69                   dst_r = interp_r;
70                   dst_g = interp_g;
71                   dst_b = interp_b;
72                   dst_a = 1.0; // implied
73              }
74         } else {
75              dst_r = 0;
76              dst_g = 0;
77              dst_b = 0;
78              dst_a = 0;
79         }
80
81
82
83       The MLIB_BLEND_GTK_SRC_OVER  or  MLIB_BLEND_GTK_SRC_OVER2  blending  is
84       similar  to  the  SRC_OVER rule of the Porter-Duff rules for image com‐
85       positing.  It is defined by
86
87         Cd = Cs + Cd*(1 - As)
88         Ad = As + Ad*(1 - As)
89
90
91
92       in general, and by the following formula for this function:
93
94         w = alpha*interp_a + (1 - alpha*interp_a)*dst_a;
95         if (w != 0.0) {
96              dst_r = (alpha*interp_r +
97                   (1 - alpha*interp_a)*dst_a*dst_r)/w;
98              dst_g = (alpha*interp_g +
99                   (1 - alpha*interp_a)*dst_a*dst_g)/w;
100              dst_b = (alpha*interp_b +
101                   (1 - alpha*interp_a)*dst_a*dst_b)/w;
102              dst_a = w;
103         } else if (MLIB_BLEND_GTK_SRC_OVER) {
104              dst_r = 0;
105              dst_g = 0;
106              dst_b = 0;
107              dst_a = 0;
108         }
109
110
111
112       where alpha, src_a, interp_a and dst_a are assumed to be in  the  range
113       of [0.0, 1.0].
114
115
116       For  an  image with 4 channels, the first or the fourth channel is con‐
117       sidered the alpha channel if cmask equals  8  or  1,  respectively.  An
118       image  with 3 channels is considered to have no alpha channel, which is
119       equivalent to having an alpha channel filled with all 1.0, or  0xff  in
120       case of MLIB_BYTE, if the general formulas for blending shown above are
121       used.
122
123
124       Both src and dst must be of type MLIB_BYTE. They can have either 3 or 4
125       channels.
126
127
128       The src image cannot have width or height larger than 32767.
129

PARAMETERS

131       The function takes the following arguments:
132
133       dst       Pointer to destination image.
134
135
136       src       Pointer to first source image.
137
138
139       zoomx     X zoom factor. zoomx > 0.0.
140
141
142       zoomy     Y zoom factor. zoomy > 0.0.
143
144
145       tx        X translation.
146
147
148       ty        Y translation.
149
150
151       filter    Type of resampling filter. It can be one of the following:
152
153                   MLIB_NEAREST
154                   MLIB_BILINEAR
155                   MLIB_BICUBIC
156                   MLIB_BICUBIC2
157
158
159
160       edge      Type of edge condition. It can be one of the following:
161
162                   MLIB_EDGE_DST_NO_WRITE
163                   MLIB_EDGE_DST_FILL_ZERO
164                   MLIB_EDGE_OP_NEAREST
165                   MLIB_EDGE_SRC_EXTEND
166                   MLIB_EDGE_SRC_EXTEND_INDEF
167                   MLIB_EDGE_SRC_PADDED
168
169
170
171       blend     Type of alpha blending. It can be one of the following:
172
173                   MLIB_BLEND_GTK_SRC
174                   MLIB_BLEND_GTK_SRC_OVER
175                   MLIB_BLEND_GTK_SRC_OVER2
176
177
178
179       alpha     Overall alpha for blending.
180
181
182       cmask     Channel mask to indicate the alpha channel.
183
184

RETURN VALUES

186       The  function  returns MLIB_SUCCESS if successful. Otherwise it returns
187       MLIB_FAILURE.
188

ATTRIBUTES

190       See attributes(5) for descriptions of the following attributes:
191
192
193
194
195       ┌─────────────────────────────┬─────────────────────────────┐
196       │      ATTRIBUTE TYPE         │      ATTRIBUTE VALUE        │
197       ├─────────────────────────────┼─────────────────────────────┤
198       │Interface Stability          │Committed                    │
199       ├─────────────────────────────┼─────────────────────────────┤
200       │MT-Level                     │MT-Safe                      │
201       └─────────────────────────────┴─────────────────────────────┘
202

NAME

SYNOPSIS

DESCRIPTION

PARAMETERS

RETURN VALUES

ATTRIBUTES

SEE ALSO