我一直在尝试在画布上加载的图像上放置滤镜(例如亮度,对比度)。 以下是我在做什么的摘要
/******Loading Image in Canvas******/
let canvas = document.getElementById('demo');
let ctx = canvas.getContext('2d');
var reader = new FileReader();
reader.onload = function(event){
var img = new Image();
img.onload = function(){
canvas.width = 220;
canvas.height = 250;
ctx.drawImage(img,0,0,canvas.width,canvas.height);
}
img.src = event.target.result;
self.oldImg = event.target.result;
}
reader.readAsDataURL(xevents.target.files[0]);
我添加了亮度,对比度逻辑,并且在图像上工作正常。 当我对图像进行任何操作(例如调整画布大小(使用可调整大小的jquery UI))时,实际上就会出现问题。应用的过滤器会丢失。 以下是调整大小后在画布上重新绘制的代码段。
$(".stretch").resizable({ resize: function(event, ui) {
$("#demo", this).each(function() {
$(this).attr({ width: ui.size.width, height: ui.size.height });
self.reDraw(this);
});
} });
reDraw () {
var img = new Image();
var canvas = document.getElementById('demo');
var c = canvas.getContext("2d");
img.src = this.oldImg;
c.drawImage(img, 0, 0, canvas.width, canvas.height);
}
我相信,由于它再次创建了一个新的图像对象(new Image()),因此过滤器已经丢失。 谁可以帮我这个事。我希望在调整画布大小时保留过滤器。
感激!谢谢
更新
process (type, amount) {
var img = new Image();
var canvas = document.getElementById('demo');
var c = canvas.getContext("2d");
img.src = this.oldImg;
c.drawImage(img, 0, 0, canvas.width, canvas.height);
let imgData = c.getImageData(0, 0, canvas.width, canvas.height);
let data = imgData.data;
if(type === 'b') {
for (let i = 0; i < data.length; i += 4) {
data[i] += amount;
data[i + 1] += amount;
data[i + 2] += amount;
}
}
if(type === 'c') {
amount = (amount/100) + 1; //convert to decimal & shift range: [0..2]
let intercept = 128 * (1 - amount);
for(let i=0;i<data.length;i+=4){ //r,g,b,a
data[i] = data[i]*amount + intercept;
data[i+1] = data[i+1]*amount + intercept;
data[i+2] = data[i+2]*amount + intercept;
}
}
c.putImageData(imgData, 0, 0);
}