使用 canvas 和透明 PNG 进行像素化调整大小
Pixelated resize using canvas with transparent PNG
我想使用 canvas 选项 imageSmoothingEnabled=false 实现像素化效果;所以图像 "unblurs" 滚动。
在使用透明图像(即 PNG)之前一切正常。投影缩放后的图像,它留在背景中。
此外,直到用户滚动几个像素后图像才会加载。
我发现 canvas.drawImage() 函数拥有设置偏移量的参数。但是我还没有找到解决办法。
演示 https://jsfiddle.net/aLjfemru/
var ctx = canvas.getContext('2d'),
img = new Image(),
play = false;
/// turn off image smoothing - this will give the pixelated effect
ctx.mozImageSmoothingEnabled = false;
ctx.webkitImageSmoothingEnabled = false;
ctx.imageSmoothingEnabled = false;
/// wait until image is actually available
img.onload = function(){
image1.src="nf.png";
context.drawImage(image1, 50, 50, 10, 10);
};
img.src = 'https://upload.wikimedia.org/wikipedia/commons/b/bb/Gorgosaurus_BW_transparent.png';
/// MAIN function
function pixelate(v) {
document.getElementById("v").innerHTML = "(v): " + v;
/// if in play mode use that value, else use slider value
var size = v * 0.01;
var w = canvas.width * size;
var h = canvas.height * size;
/// draw original image to the scaled size
ctx.clearRect(0, 0, canvas.width, canvas.height);
ctx.drawImage(img, 0, 0, w, h);
ctx.drawImage(canvas, 0, 0, w, h, 0, 0, canvas.width, canvas.height);
}
function onScroll() {
$(window).on('scroll', function() {
var y = window.pageYOffset;
if (y > 10) {
y = Math.pow(y, 0.8);
if (y >= 60) {
y = 100;
}
pixelate(y);
}
});
}
onScroll();
一些快速的改变来实现它
用第二个canvas做像素化
在进行渲染之前等待图像加载。
onscroll 在你滚动之前不会触发,所以当图像加载后调用渲染函数来显示图像。
canvas.width = innerWidth-20;
ctx = canvas.getContext("2d");
var ctxImage;
const img = new Image;
img.src = 'https://upload.wikimedia.org/wikipedia/commons/b/bb/Gorgosaurus_BW_transparent.png';
/// wait until image is actually available
img.onload = function(){
// I dont knwo what this is for so removed the following two lines
//image1.src="nf.png";
//context.drawImage(image1, 50, 50, 10, 10);
// Create a canvas to match the image
var c = document.createElement("canvas");
canvas.width = Math.min(canvas.width,(c.width = this.naturalWidth));
canvas.height = c.height = this.naturalHeight;
ctxImage = c.getContext("2d");
// changing canvas size resets the state so need to set this again.
ctx.imageSmoothingEnabled = false;
onScroll();
pixelate(100); // call first time
};
ctx.font = "32px arial";
ctx.textAlign = "center";
ctx.fillText("Loading please wait.",ctx.canvas.width /2, ctx.canvas.height / 4);
/// MAIN function
function pixelate(v) {
document.getElementById("v").innerHTML = "(v): " + v;
/// if in play mode use that value, else use slider value
var size = Number(v) * 0.01;
var w = img.width * size;
var h = img.height * size;
ctx.clearRect(0, 0, canvas.width, canvas.height);
ctxImage.clearRect(0, 0, ctxImage.canvas.width, ctxImage.canvas.height);
ctxImage.drawImage(img, 0, 0, w, h);
ctx.drawImage(ctxImage.canvas, 0, 0, w, h, 0, 0, canvas.width, canvas.height);
}
function onScroll() {
addEventListener("scroll", function() {
var y = window.pageYOffset;
if (y > 10) {
y = Math.pow(y, 0.65);
if (y >= 100) {
y = 100;
}
pixelate(y);
}
});
}
#fix {
position: fixed;
}
html {
height: 2000px;
}
<div id="fix">
<p id="v" value="Animate">1</p><br />
<canvas id="canvas"></canvas>
</div>
这已经成为一个极简主义的库,可以找到我对 PNG 支持的 PR here。
合并后我会回来更新这个答案。
来自@Blindman67 的回答的完整代码,概括和简化:
/**
* 8bit
*
* A module that converts an image into a pixelated version (just like
* 8bit artwork).
*
* @author rogeriopvl <https://github.com/rogeriopvl>
* @license MIT
*/
(function (root, factory) {
if (typeof define === "function" && define.amd) {
define([], factory);
} else if (typeof exports === "object") {
module.exports = factory();
} else {
root.eightBit = factory();
}
} (this, function () {
// Necessary to hide the original image with PNG transparency
const invisibleCanvas = document.createElement("canvas");
const invisibleCtx = invisibleCanvas.getContext("2d");
/**
* Draws a pixelated version of an image in a given canvas.
* @param {object} canvas - a canvas object
* @param {object} image - an image HTMLElement object
* @param {number} quality - the new quality: between 0 and 100
*/
const eightBit = function (canvas, image, quality) {
quality /= 100;
canvas.width = invisibleCanvas.width = image.width;
canvas.height = invisibleCanvas.height = image.height;
const scaledW = canvas.width * quality;
const scaledH = canvas.height * quality;
const ctx = canvas.getContext("2d");
ctx.mozImageSmoothingEnabled = false;
ctx.webkitImageSmoothingEnabled = false;
ctx.imageSmoothingEnabled = false;
// Draws image scaled to desired quality on the invisible canvas, then
// draws that scaled image on the visible canvas.
ctx.clearRect(0, 0, canvas.width, canvas.height);
invisibleCtx.clearRect(0, 0, invisibleCtx.canvas.width, invisibleCtx.canvas.height);
invisibleCtx.drawImage(image, 0, 0, scaledW, scaledH);
ctx.drawImage(invisibleCtx.canvas, 0, 0, scaledW, scaledH, 0, 0, canvas.width, canvas.height);
};
return eightBit;
}));
我想使用 canvas 选项 imageSmoothingEnabled=false 实现像素化效果;所以图像 "unblurs" 滚动。
在使用透明图像(即 PNG)之前一切正常。投影缩放后的图像,它留在背景中。
此外,直到用户滚动几个像素后图像才会加载。
我发现 canvas.drawImage() 函数拥有设置偏移量的参数。但是我还没有找到解决办法。
演示 https://jsfiddle.net/aLjfemru/
var ctx = canvas.getContext('2d'),
img = new Image(),
play = false;
/// turn off image smoothing - this will give the pixelated effect
ctx.mozImageSmoothingEnabled = false;
ctx.webkitImageSmoothingEnabled = false;
ctx.imageSmoothingEnabled = false;
/// wait until image is actually available
img.onload = function(){
image1.src="nf.png";
context.drawImage(image1, 50, 50, 10, 10);
};
img.src = 'https://upload.wikimedia.org/wikipedia/commons/b/bb/Gorgosaurus_BW_transparent.png';
/// MAIN function
function pixelate(v) {
document.getElementById("v").innerHTML = "(v): " + v;
/// if in play mode use that value, else use slider value
var size = v * 0.01;
var w = canvas.width * size;
var h = canvas.height * size;
/// draw original image to the scaled size
ctx.clearRect(0, 0, canvas.width, canvas.height);
ctx.drawImage(img, 0, 0, w, h);
ctx.drawImage(canvas, 0, 0, w, h, 0, 0, canvas.width, canvas.height);
}
function onScroll() {
$(window).on('scroll', function() {
var y = window.pageYOffset;
if (y > 10) {
y = Math.pow(y, 0.8);
if (y >= 60) {
y = 100;
}
pixelate(y);
}
});
}
onScroll();
一些快速的改变来实现它
用第二个canvas做像素化
在进行渲染之前等待图像加载。
onscroll 在你滚动之前不会触发,所以当图像加载后调用渲染函数来显示图像。
canvas.width = innerWidth-20;
ctx = canvas.getContext("2d");
var ctxImage;
const img = new Image;
img.src = 'https://upload.wikimedia.org/wikipedia/commons/b/bb/Gorgosaurus_BW_transparent.png';
/// wait until image is actually available
img.onload = function(){
// I dont knwo what this is for so removed the following two lines
//image1.src="nf.png";
//context.drawImage(image1, 50, 50, 10, 10);
// Create a canvas to match the image
var c = document.createElement("canvas");
canvas.width = Math.min(canvas.width,(c.width = this.naturalWidth));
canvas.height = c.height = this.naturalHeight;
ctxImage = c.getContext("2d");
// changing canvas size resets the state so need to set this again.
ctx.imageSmoothingEnabled = false;
onScroll();
pixelate(100); // call first time
};
ctx.font = "32px arial";
ctx.textAlign = "center";
ctx.fillText("Loading please wait.",ctx.canvas.width /2, ctx.canvas.height / 4);
/// MAIN function
function pixelate(v) {
document.getElementById("v").innerHTML = "(v): " + v;
/// if in play mode use that value, else use slider value
var size = Number(v) * 0.01;
var w = img.width * size;
var h = img.height * size;
ctx.clearRect(0, 0, canvas.width, canvas.height);
ctxImage.clearRect(0, 0, ctxImage.canvas.width, ctxImage.canvas.height);
ctxImage.drawImage(img, 0, 0, w, h);
ctx.drawImage(ctxImage.canvas, 0, 0, w, h, 0, 0, canvas.width, canvas.height);
}
function onScroll() {
addEventListener("scroll", function() {
var y = window.pageYOffset;
if (y > 10) {
y = Math.pow(y, 0.65);
if (y >= 100) {
y = 100;
}
pixelate(y);
}
});
}
#fix {
position: fixed;
}
html {
height: 2000px;
}
<div id="fix">
<p id="v" value="Animate">1</p><br />
<canvas id="canvas"></canvas>
</div>
这已经成为一个极简主义的库,可以找到我对 PNG 支持的 PR here。
合并后我会回来更新这个答案。
来自@Blindman67 的回答的完整代码,概括和简化:
/**
* 8bit
*
* A module that converts an image into a pixelated version (just like
* 8bit artwork).
*
* @author rogeriopvl <https://github.com/rogeriopvl>
* @license MIT
*/
(function (root, factory) {
if (typeof define === "function" && define.amd) {
define([], factory);
} else if (typeof exports === "object") {
module.exports = factory();
} else {
root.eightBit = factory();
}
} (this, function () {
// Necessary to hide the original image with PNG transparency
const invisibleCanvas = document.createElement("canvas");
const invisibleCtx = invisibleCanvas.getContext("2d");
/**
* Draws a pixelated version of an image in a given canvas.
* @param {object} canvas - a canvas object
* @param {object} image - an image HTMLElement object
* @param {number} quality - the new quality: between 0 and 100
*/
const eightBit = function (canvas, image, quality) {
quality /= 100;
canvas.width = invisibleCanvas.width = image.width;
canvas.height = invisibleCanvas.height = image.height;
const scaledW = canvas.width * quality;
const scaledH = canvas.height * quality;
const ctx = canvas.getContext("2d");
ctx.mozImageSmoothingEnabled = false;
ctx.webkitImageSmoothingEnabled = false;
ctx.imageSmoothingEnabled = false;
// Draws image scaled to desired quality on the invisible canvas, then
// draws that scaled image on the visible canvas.
ctx.clearRect(0, 0, canvas.width, canvas.height);
invisibleCtx.clearRect(0, 0, invisibleCtx.canvas.width, invisibleCtx.canvas.height);
invisibleCtx.drawImage(image, 0, 0, scaledW, scaledH);
ctx.drawImage(invisibleCtx.canvas, 0, 0, scaledW, scaledH, 0, 0, canvas.width, canvas.height);
};
return eightBit;
}));