1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
|
// These patterns are used by the pattern dither effect
(function(){
var patterns = {}
patterns[2] = [ 0, 2,
3, 1 ]
patterns[3] = [ 0, 5, 3,
8, 1, 6,
4, 7, 2, ]
patterns[4] = [ 0, 8, 2, 10,
6, 14, 4, 12,
3, 11, 1, 9,
5, 13, 7, 15 ]
CanvasQuery.Wrapper.prototype.pattern2Dither = function() {
this.patternDither(patterns[2])
}
CanvasQuery.Wrapper.prototype.pattern3Dither = function() {
this.patternDither(patterns[3])
}
CanvasQuery.Wrapper.prototype.pattern4Dither = function() {
this.patternDither(patterns[4])
}
CanvasQuery.Wrapper.prototype.pattern2LiteDither = function() {
this.patternLiteDither(patterns[2])
}
CanvasQuery.Wrapper.prototype.pattern3LiteDither = function() {
this.patternLiteDither(patterns[3])
}
CanvasQuery.Wrapper.prototype.pattern4LiteDither = function() {
this.patternLiteDither(patterns[4])
}
})()
// Threshold dither, black if less than n, white otherwise
CanvasQuery.Wrapper.prototype.threshold = function(n) {
var bitmap = this.context.getImageData(0, 0, this.canvas.width, this.canvas.height)
var bitmapData = bitmap.data
var width = this.canvas.width
var height = this.canvas.height
if (n < 1) n *= 255
for (var i = 0; i < height; i++) {
for (var j = 0; j < width; j++) {
var a = 4 * (i*width + j)
var val = (bitmapData[a] + bitmapData[a+1] + bitmapData[a+2]) / 3
var lum = val > n ? 255 : 0
bitmapData[a] = bitmapData[a+1] = bitmapData[a+2] = lum
}
}
this.context.putImageData(bitmap, 0, 0);
return this;
}
// Random dither, black if less than a random number (chosen per pixel), white otherwise
CanvasQuery.Wrapper.prototype.randomDither = function() {
var bitmap = this.context.getImageData(0, 0, this.canvas.width, this.canvas.height)
var bitmapData = bitmap.data
var width = this.canvas.width
var height = this.canvas.height
for (var i = 0; i < height; i++) {
for (var j = 0; j < width; j++) {
var a = 4 * (i*width + j)
var val = (bitmapData[a] + bitmapData[a+1] + bitmapData[a+2]) / (3*255)
var lum = val > Math.random() ? 255 : 0
bitmapData[a] = bitmapData[a+1] = bitmapData[a+2] = lum
}
}
this.context.putImageData(bitmap, 0, 0);
return this;
}
// Pattern dither, uses a square matrix of dither steps (see patterns above) to dither
CanvasQuery.Wrapper.prototype.patternDither = function(pattern) {
var bitmap = this.context.getImageData(0, 0, this.canvas.width, this.canvas.height)
var bitmapData = bitmap.data
var width = this.canvas.width
var height = this.canvas.height
var n = Math.floor(Math.sqrt(pattern.length))
var len = pattern.length - 1
for (var i = 0; i < height; i++) {
for (var j = 0; j < width; j++) {
var p = ((i % n) * n) + (j % n)
var a = 4 * (i*width + j)
var val = (bitmapData[a] + bitmapData[a+1] + bitmapData[a+2]) / (3*255)
var lum = val > pattern[p]/len ? 255 : 0
bitmapData[a] = bitmapData[a+1] = bitmapData[a+2] = lum
}
}
this.context.putImageData(bitmap, 0, 0);
return this;
}
// Light version of pattern dither, uses the wrong array size
CanvasQuery.Wrapper.prototype.patternLiteDither = function(pattern) {
var bitmap = this.context.getImageData(0, 0, this.canvas.width, this.canvas.height)
var bitmapData = bitmap.data
var width = this.canvas.width
var height = this.canvas.height
var n = Math.floor(Math.sqrt(pattern.length))
var len = pattern.length
for (var i = 0; i < height; i++) {
for (var j = 0; j < width; j++) {
var p = ((i % n) * n) + (j % n)
var a = 4 * (i*width + j)
var val = (bitmapData[a] + bitmapData[a+1] + bitmapData[a+2]) / (3*255)
var lum = val > pattern[p]/len ? 255 : 0
bitmapData[a] = bitmapData[a+1] = bitmapData[a+2] = lum
}
}
this.context.putImageData(bitmap, 0, 0);
return this;
}
// Floyd-Steinberg error diffusion, propagates error down and to the right
CanvasQuery.Wrapper.prototype.floydSteinbergDither = function(n) {
var bitmap = this.context.getImageData(0, 0, this.canvas.width, this.canvas.height)
var bitmapData = bitmap.data
var mask = this.grayscaleToMask()
var width = this.canvas.width
var height = this.canvas.height
for (var y = 0; y < height; y++) {
for (var x = 0; x < width; x++) {
var p = (y*width + x)
var a = 4 * p
var val = mask[p]
var lum = val > 127 ? 255 : 0
var error = val - lum
if (x < width-1)
mask[ (y*width) + x+1 ] += 7/16 * error
if (y < height-1 && x > 0)
mask[ ((y+1)*width) + x-1 ] += 5/16 * error
if (y < height-1)
mask[ ((y+1)*width) + x ] += 3/16 * error
if (y < height-1 && x < width-1)
mask[ ((y+1)*width) + x+1 ] += 1/16 * error
bitmapData[a] = bitmapData[a+1] = bitmapData[a+2] = lum
}
}
this.context.putImageData(bitmap, 0, 0);
return this;
}
// Rightwise diffusion dither, propagates error to the right only
CanvasQuery.Wrapper.prototype.rightDither = function(n) {
var bitmap = this.context.getImageData(0, 0, this.canvas.width, this.canvas.height)
var bitmapData = bitmap.data
var mask = this.grayscaleToMask()
var width = this.canvas.width
var height = this.canvas.height
for (var y = 0; y < height; y++) {
for (var x = 0; x < width; x++) {
var p = (y*width + x)
var a = 4 * p
var val = mask[p]
var lum = val > 127 ? 255 : 0
var error = val - lum
if (x < width-1)
mask[ (y*width) + x+1 ] += 7/16 * error
bitmapData[a] = bitmapData[a+1] = bitmapData[a+2] = lum
}
}
this.context.putImageData(bitmap, 0, 0);
return this;
}
// Print-style halftone effect
CanvasQuery.Wrapper.prototype.halftone = function(radius, angle) {
var mask = this.grayscaleToMask()
this.fillStyle("#fff")
this.fillRect(0, 0, this.canvas.width, this.canvas.height)
var diameter = radius*2
var TWO_PI = Math.PI*2
var angle = angle / 180 * Math.PI
var cos = Math.cos(angle)
var sin = Math.sin(angle)
var xstep = cos * radius
var ystep = sin * radius
var w = this.canvas.width
var h = this.canvas.height
this.fillStyle("#000")
for (var i = -w; i < w; i++) {
for (var j = -h; j < h; j++) {
var x = i * ystep - j * xstep
var y = i * xstep + j * ystep
if (x > -diameter && y > -diameter && x < w+diameter && y < h+diameter) {
circle(this,x,y)
}
}
}
function circle(cq,x,y) {
var xx = x < 0 ? 0 : x > w ? w - 1 : x;
var yy = y < 0 ? 0 : y > h ? h - 1 : y;
var r = (1 - Math.pow( mask[ ~~(~~yy*w+(xx)) ] / 255, Math.E/4 )) * radius
cq.beginPath()
.arc(x,y,r,0,TWO_PI)
.closePath()
.fill();
}
return this;
}
|
