[英]Crop image via finger(touch) in Ionic App
指针事件在移动设备中不起作用,因此这是在Ionic应用程序或任何跨平台应用程序中完成一些修改的代码。
setTimeout(example,0); // ensures that the run us after parsing
function example(){
const ctx = canvas.getContext("2d");
var w = canvas.width;
var h = canvas.height;
var cw = w / 2; // center
var ch = h / 2;
var selectLayer = CImageCtx(w,h); // creates a canvas
var selectedContent = CImageCtx(w,h); // the selected content
document.getElementById("exampleEle").appendChild(selectedContent);
var image = new Image; // the image
//image.src = "img/temp.png";
image.src ="https://upload.wikimedia.org/wikipedia/commons/thumb/e/e9/Official_portrait_of_Barack_Obama.jpg/220px-Official_portrait_of_Barack_Obama.jpg";
// updates the masked result
function updateSelected(){
var ctx = selectedContent.ctx;
ctx.drawImage(image,0,0);
ctx.globalCompositeOperation = "destination-in";
ctx.drawImage(selectLayer,0,0);
ctx.globalCompositeOperation = "source-over";
}
function update(){
// if mouse down then
if(touch.but){
// clear the mask if on the right image
if(touch.oldBut === false && touch.x > 256){
selectLayer.ctx.clearRect(0,0,w,h);
touch.but = false;
}else{
// draw the red
selectLayer.ctx.fillStyle = "red";
fillCircle(touch.x, touch.y, 20, selectLayer.ctx);
}
// update the masked result
updateSelected();
}
// clear the canvas
ctx.clearRect(0,0,w,h);
// draw the image
ctx.drawImage(image,0,0);
// then draw the marking layer over it with comp overlay
ctx.globalCompositeOperation = "overlay";
ctx.drawImage(selectLayer,0,0);
ctx.globalCompositeOperation = "source-over";
touch.oldBut = touch.but;
requestAnimationFrame(update);
}
requestAnimationFrame(update);
}
//#############################################################################
// helper functions not part of the answer
//#############################################################################
const touch = {
x : 0, y : 0, but : false,
events(e){
console.log("e.type",e);
const m = touch;
const bounds = canvas.getBoundingClientRect();
var rect = e.target.getBoundingClientRect();
if(e.targetTouches) {
X = parseInt(e.targetTouches[0].pageX - rect.left);
Y = parseInt(e.targetTouches[0].pageY - rect.top);
}
m.x = X;
m.y = Y;
m.but = e.type === "touchstart" ? true : e.type === "touchend" ? false : m.but;
}
};
(["start","end","move"]).forEach(name => document.addEventListener("touch" + name,touch.events));
const CImage = (w = 128, h = w) => (c = document.createElement("canvas"),c.width = w,c.height = h, c);
const CImageCtx = (w = 128, h = w) => (c = CImage(w,h), c.ctx = c.getContext("2d"), c);
const fillCircle = (l,y=ctx,r=ctx,c=ctx) =>{if(l.p1){c=y; r=leng(l);y=l.p1.y;l=l.p1.x }else if(l.x){c=r;r=y;y=l.y;l=l.x}c.beginPath(); c.arc(l,y,r,0,Math.PI*2); c.fill()}
而对于视图你必须添加这3行HTML。
<div id="exampleEle">
<canvas id="canvas" width=256 height=256></canvas>
</div>
基本上我不是离子开发者但谷歌搜索后发现一些可能对你有帮助的代码。
setTimeout(example,0); // ensures that the run us after parsing function example(){ const ctx = canvas.getContext("2d"); var w = canvas.width; var h = canvas.height; var cw = w / 2; // center var ch = h / 2; var selectLayer = CImageCtx(w,h); // creates a canvas var selectedContent = CImageCtx(w,h); // the selected content document.body.appendChild(selectedContent); var image = new Image; // the image image.src ="https://upload.wikimedia.org/wikipedia/commons/thumb/e/e9/Official_portrait_of_Barack_Obama.jpg/220px-Official_portrait_of_Barack_Obama.jpg"; // updates the masked result function updateSelected(){ var ctx = selectedContent.ctx; ctx.drawImage(image,0,0); ctx.globalCompositeOperation = "destination-in"; ctx.drawImage(selectLayer,0,0); ctx.globalCompositeOperation = "source-over"; } function update(){ // if mouse down then if(mouse.but){ // clear the mask if on the right image if(mouse.oldBut === false && mouse.x > 256){ selectLayer.ctx.clearRect(0,0,w,h); mouse.but = false; }else{ // draw the red selectLayer.ctx.fillStyle = "red"; fillCircle(mouse.x, mouse.y, 10, selectLayer.ctx); } // update the masked result updateSelected(); } // clear the canvas ctx.clearRect(0,0,w,h); // draw the image ctx.drawImage(image,0,0); // then draw the marking layer over it with comp overlay ctx.globalCompositeOperation = "overlay"; ctx.drawImage(selectLayer,0,0); ctx.globalCompositeOperation = "source-over"; mouse.oldBut = mouse.but; requestAnimationFrame(update); } requestAnimationFrame(update); } const mouse = { x : 0, y : 0, but : false, events(e){ const m = mouse; const bounds = canvas.getBoundingClientRect(); mx = e.pageX - bounds.left - scrollX; my = e.pageY - bounds.top - scrollY; m.but = e.type === "pointerdown" ? true : e.type === "pointerup" ? false : m.but; } }; document.addEventListener('pointerdown', mouse.events); document.addEventListener('pointerup', mouse.events); document.addEventListener('pointermove', mouse.events); const CImage = (w = 128, h = w) => (c = document.createElement("canvas"),c.width = w,c.height = h, c); const CImageCtx = (w = 128, h = w) => (c = CImage(w,h), c.ctx = c.getContext("2d"), c); const fillCircle = (l,y=ctx,r=ctx,c=ctx) =>{if(l.p1){c=y; r=leng(l);y=l.p1.y;l=l.p1.x }else if(lx){c=r;r=y;y=ly;l=lx}c.beginPath(); c.arc(l,y,r,0,Math.PI*2); c.fill()}
Draw on image and the selected parts are shown on the right<br> Click right image to reset selection<br> <canvas id="canvas" width=256 height=256></canvas>
选中以运行代码段。
你需要
从'ionic-native'导入{CropPlugin};
您可以查看https://github.com/alexk111/ngImgCrop和https://github.com/jeduan/cordova-plugin-crop
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