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这是一个很有意思的特效,模拟摄像机拍摄电视屏幕画面时出现点状颗粒的效果。颗粒的大小通过变换矩阵实现,可以任意调节,有兴趣研究的朋友可以尝试更多的效果,代码没有经过优化,只是一个粗糙的Demo,大家可以自行改进。
1 2 3 4 5 6 | img.src = ’http: //bloglaotou.duapp.com/wp-content/themes/frontopen2/tools/filter/p_w_picpath3.jpg’; canvas.width = img.width; canvas.height = img.height; var context = canvas.getContext(“2d”); context.drawImage(img, 0, 0); var canvasData = context.getImageData(0, 0, canvas.width, canvas.height); |
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 | var m_VideoType=0;
var pattern= new Array();
switch (m_VideoType)
{
case0: //VIDEO_TYPE.VIDEO_STAGGERED:
{
pattern = [
0, 1,
0, 2,
1, 2,
1, 0,
2, 0,
2, 1,
];
break ;
}
case1: //VIDEO_TYPE.VIDEO_TRIPED:
{
pattern = [
0,
1,
2,
];
break ;
}
case2: //VIDEO_TYPE.VIDEO_3X3:
{
pattern =
[
0, 1, 2,
2, 0, 1,
1, 2, 0,
];
break ;
}
default :
{
pattern =
[
0, 1, 2, 0, 0,
1, 1, 1, 2, 0,
0, 1, 2, 2, 2,
0, 0, 1, 2, 0,
0, 1, 1, 1, 2,
2, 0, 1, 2, 2,
0, 0, 0, 1, 2,
2, 0, 1, 1, 1,
2, 2, 0, 1, 2,
2, 0, 0, 0, 1,
1, 2, 0, 1, 1,
2, 2, 2, 0, 1,
1, 2, 0, 0, 0,
1, 1, 2, 0, 1,
1, 2, 2, 2, 0,
];
break ;
}
}
var pattern_width = [ 2, 1, 3, 5 ];
var pattern_height = [6, 3, 3, 15 ]; |
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 | for ( var x = 0; x < canvasData.width; x++) {
for ( var y = 0; y < canvasData.height; y++) {
// Index of the pixel in the array
var idx = (x + y * canvasData.width) * 4;
var r = canvasData.data[idx + 0];
var g = canvasData.data[idx + 1];
var b = canvasData.data[idx + 2];
var nWidth = pattern_width[m_VideoType];
var nHeight = pattern_height[m_VideoType];
var index = nWidth * (y % nHeight) + (x % nWidth);
index = pattern[index];
if (index == 0)
var r = fclamp0255(2 * r);
if (index == 1)
var g = fclamp0255(2 * g);
if (index == 2)
var b = fclamp0255(2 * b);
// assign gray scale value
canvasData.data[idx + 0] = r; // Red channel
canvasData.data[idx + 1] = g; // Green channel
canvasData.data[idx + 2] = b; // Blue channel
canvasData.data[idx + 3] = 255; // Alpha channel
// 加上黑色的边框
if (x < 8 || y < 8 || x > (canvasData.width - 8) || y > (canvasData.height - 8))
{
canvasData.data[idx + 0] = 0;
canvasData.data[idx + 1] = 0;
canvasData.data[idx + 2] = 0;
}
}
} |
1 | context.putImageData(canvasData, 0, 0); |
点击这里预览
代震军ImageFilter开源项目
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