1 /*
2 Copyright (c) 2011-2021 Timur Gafarov
3
4 Boost Software License - Version 1.0 - August 17th, 2003
5
6 Permission is hereby granted, free of charge, to any person or organization
7 obtaining a copy of the software and accompanying documentation covered by
8 this license (the "Software") to use, reproduce, display, distribute,
9 execute, and transmit the Software, and to prepare derivative works of the
10 Software, and to permit third-parties to whom the Software is furnished to
11 do so, all subject to the following:
12
13 The copyright notices in the Software and this entire statement, including
14 the above license grant, this restriction and the following disclaimer,
15 must be included in all copies of the Software, in whole or in part, and
16 all derivative works of the Software, unless such copies or derivative
17 works are solely in the form of machine-executable object code generated by
18 a source language processor.
19
20 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
21 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
22 FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
23 SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
24 FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
25 ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
26 DEALINGS IN THE SOFTWARE.
27 */
28
29 /**
30 * Image convolution
31 *
32 * Copyright: Timur Gafarov 2011-2021.
33 * License: $(LINK2 boost.org/LICENSE_1_0.txt, Boost License 1.0).
34 * Authors: Timur Gafarov
35 */
36 module dlib.image.filters.convolution;
37
38 import std.algorithm;
39 import dlib.image.image;
40 import dlib.image.color;
41
42 /// Convolve an image with a kernel
43 SuperImage convolve(SuperImage img,
44 SuperImage outp,
45 float[] kernel,
46 uint kw = 3,
47 uint kh = 3,
48 float divisor = 1.0f,
49 float offset = 0.5f,
50 bool normalize = true,
51 bool useAlpha = true)
52 in
53 {
54 assert(img.data.length);
55 assert(kernel.length == kw * kh);
56 }
57 do
58 {
59 SuperImage res;
60 if (outp)
61 res = outp;
62 else
63 res = img.dup;
64
65 float kernelSum = reduce!((a,b) => a + b)(kernel);
66
67 foreach(y; 0..img.height)
68 foreach(x; 0..img.width)
69 {
70 float alpha = Color4f(img[x, y]).a;
71
72 Color4f csum = Color4f(0, 0, 0);
73
74 foreach(ky; 0..kh)
75 foreach(kx; 0..kw)
76 {
77 int iy = y + (ky - kh/2);
78 int ix = x + (kx - kw/2);
79
80 // Extend
81 if (ix < 0) ix = 0;
82 if (ix >= img.width) ix = img.width - 1;
83 if (iy < 0) iy = 0;
84 if (iy >= img.height) iy = img.height - 1;
85
86 // TODO:
87 // Wrap
88
89 auto pix = Color4f(img[ix, iy]);
90 auto k = kernel[kx + ky * kw];
91
92 csum += pix * k;
93 }
94
95 if (normalize)
96 {
97 offset = 0.0f;
98 divisor = kernelSum;
99
100 if (divisor == 0.0f)
101 {
102 divisor = 1.0f;
103 offset = 0.5f;
104 }
105
106 if (divisor < 0.0f)
107 offset = 1.0f;
108 }
109
110 csum = csum / divisor + offset;
111
112 if (!useAlpha)
113 csum.a = alpha;
114
115 res[x,y] = csum;
116 }
117
118 return res;
119 }
120
121 /// ditto
122 SuperImage convolve(SuperImage img,
123 float[] kernel,
124 uint kw = 3,
125 uint kh = 3,
126 float divisor = 1.0f,
127 float offset = 0.5f,
128 bool normalize = true,
129 bool useAlpha = true)
130 {
131 return convolve(img, null, kernel, kw, kh, divisor, offset, normalize, useAlpha);
132 }
133
134 /// Various built-in convolution kernels
135 struct Kernel
136 {
137 enum float[]
138
139 Identity =
140 [
141 0, 0, 0,
142 0, 1, 0,
143 0, 0, 0
144 ],
145
146 BoxBlur =
147 [
148 1, 1, 1,
149 1, 1, 1,
150 1, 1, 1
151 ],
152
153 GaussianBlur =
154 [
155 1, 2, 1,
156 2, 4, 2,
157 1, 2, 1
158 ],
159
160 Sharpen =
161 [
162 -1, -1, -1,
163 -1, 11, -1,
164 -1, -1, -1
165 ],
166
167 Emboss =
168 [
169 -1, -1, 0,
170 -1, 0, 1,
171 0, 1, 1,
172 ],
173
174 EdgeEmboss =
175 [
176 -1.0f, -0.5f, -0.0f,
177 -0.5f, 1.0f, 0.5f,
178 -0.0f, 0.5f, 1.0f
179 ],
180
181 EdgeDetect =
182 [
183 -1, -1, -1,
184 -1, 8, -1,
185 -1, -1, -1,
186 ],
187
188 Laplace =
189 [
190 0, 1, 0,
191 1, -4, 1,
192 0, 1, 0,
193 ];
194 }