[英]Resizing a canvas image without blurring it
I have a small image, which I am rendering on a canvas, like this: 我有一个小图像,我在画布上渲染,像这样:
ctx.drawImage(img, 0, 0, img.width*2, img.height*2);
I would like this to show a sharp upsized image (4 identical pixels for each image pixel). 我希望这能显示一个急剧增大的图像(每个图像像素有4个相同的像素)。 However, this code (in Chrome 29 on Mac) makes a blurry image.
但是,此代码(在Mac上的Chrome 29中)会产生模糊的图像。 In Photoshop terms, it looks like it's using "Bicubic" resampling, instead of "Nearest Neighbour".
在Photoshop术语中,它看起来像是使用“Bicubic”重采样,而不是“最近邻”。
In a situation where it would be useful (eg. a retro game), Is it possible to produce a sharp upsized image, or do I need to have a seperate image file for each size of the image on the server? 在它有用的情况下(例如复古游戏),是否有可能产生锐化的图像,或者我是否需要为服务器上的每个图像大小分别创建一个图像文件?
Simply turn off canvas' anti-aliasing for images - unfortunately this property is still vendor prefixed so here are the variations: 简单地关闭画布'抗锯齿图像 - 不幸的是这个属性仍然是供应商前缀,所以这里是变化:
context.webkitImageSmoothingEnabled = false;
context.mozImageSmoothingEnabled = false;
context.imageSmoothingEnabled = false;
then draw the image. 然后绘制图像。
Optionally for older versions and browsers which hasn't implemented this yet, you can use CSS instead: 对于尚未实现此功能的旧版本和浏览器,您可以选择使用CSS:
canvas {
image-rendering: optimizeSpeed; // Older versions of FF
image-rendering: -moz-crisp-edges; // FF 6.0+
image-rendering: -webkit-optimize-contrast; // Webkit (non standard naming)
image-rendering: -o-crisp-edges; // OS X & Windows Opera (12.02+)
image-rendering: crisp-edges; // Possible future browsers.
-ms-interpolation-mode: nearest-neighbor; // IE (non standard naming)
}
Check this fiddle: http://jsfiddle.net/yPFjg/ 检查这个小提琴: http : //jsfiddle.net/yPFjg/
It loads the image into a canvas, then creates a resized copy and uses that as sprite. 它将图像加载到画布中,然后创建一个调整大小的副本并将其用作精灵。
With few modifications, you can implement an image loader that resizes images on the fly. 只需很少的修改,您就可以实现一个图像加载器,可以动态调整图像大小。
var ctx = document.getElementById('canvas1').getContext('2d');
var img = new Image();
var original = document.createElement("canvas");
var scaled = document.createElement("canvas");
img.onload = function() {
var oc = original.getContext('2d');
var sc = scaled.getContext('2d');
oc.canvas.width = oc.canvas.height = 16;
sc.canvas.width = sc.canvas.height = 32;
oc.drawImage(this, 0, 0);
var od = oc.getImageData(0,0,16,16);
var sd = sc.getImageData(0,0,32,32);
for (var x=0; x<32; x++) {
for (var y=0; y<32; y++) {
for (var c=0; c<4; c++) {
// you can improve these calculations, I let them so for clarity
sd.data[(y*32+x)*4+c] = od.data[((y>>1)*16+(x>>1))*4+c];
}
}
}
sc.putImageData(sd, 0, 0);
ctx.drawImage(scaled, 0, 0);
}
img.src = document.getElementById('sprite').src;
Some notes about getImageData: it returns an object with an array. 关于getImageData的一些注意事项:它返回一个带数组的对象。 The array has a height*width*4 size.
该阵列的高度为*宽* 4。 The color components are stored in RGBA order (red, green, blue, alpha, 8 bits each value).
颜色分量以RGBA顺序存储(红色,绿色,蓝色,alpha,每个值8位)。
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