(function(f){if(typeof exports==="object"&&typeof module!=="undefined"){module.exports=f()}else if(typeof define==="function"&&define.amd){define([],f)}else{var g;if(typeof window!=="undefined"){g=window}else if(typeof global!=="undefined"){g=global}else if(typeof self!=="undefined"){g=self}else{g=this}g.Perspective = f()}})(function(){var define,module,exports;return (function e(t,n,r){function s(o,u){if(!n[o]){if(!t[o]){var a=typeof require=="function"&&require;if(!u&&a)return a(o,!0);if(i)return i(o,!0);var f=new Error("Cannot find module '"+o+"'");throw f.code="MODULE_NOT_FOUND",f}var l=n[o]={exports:{}};t[o][0].call(l.exports,function(e){var n=t[o][1][e];return s(n?n:e)},l,l.exports,e,t,n,r)}return n[o].exports}var i=typeof require=="function"&&require;for(var o=0;o<r.length;o++)s(r[o]);return s})({1:[function(require,module,exports){
// Copyright 2010 futomi http://www.html5.jp/
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// perspective.js v0.0.2
// 2010-08-28
//
// This file was modified by Fabien LOISON <http://www.flozz.fr/>
/* -------------------------------------------------------------------
* define objects (name space) for this library.
* ----------------------------------------------------------------- */
var html5jp = window.html5jp || {};
(function() {
/* -------------------------------------------------------------------
* constructor
* ----------------------------------------------------------------- */
html5jp.perspective = function(ctxd, image) {
// check the arguments
if( ! ctxd || ! ctxd.strokeStyle ) { return; }
if( ! image || ! image.width || ! image.height ) { return; }
// prepare a <canvas> for the image
var cvso = document.createElement('canvas');
cvso.width = parseInt(image.width);
cvso.height = parseInt(image.height);
var ctxo = cvso.getContext('2d');
ctxo.drawImage(image, 0, 0, cvso.width, cvso.height);
// prepare a <canvas> for the transformed image
var cvst = document.createElement('canvas');
cvst.width = ctxd.canvas.width;
cvst.height = ctxd.canvas.height;
var ctxt = cvst.getContext('2d');
// parameters
this.p = {
ctxd: ctxd,
cvso: cvso,
ctxo: ctxo,
ctxt: ctxt
}
};
/* -------------------------------------------------------------------
* prototypes
* ----------------------------------------------------------------- */
var proto = html5jp.perspective.prototype;
/* -------------------------------------------------------------------
* public methods
* ----------------------------------------------------------------- */
proto.draw = function(points) {
var d0x = points[0][0];
var d0y = points[0][1];
var d1x = points[1][0];
var d1y = points[1][1];
var d2x = points[2][0];
var d2y = points[2][1];
var d3x = points[3][0];
var d3y = points[3][1];
// compute the dimension of each side
var dims = [
Math.sqrt( Math.pow(d0x-d1x, 2) + Math.pow(d0y-d1y, 2) ), // top side
Math.sqrt( Math.pow(d1x-d2x, 2) + Math.pow(d1y-d2y, 2) ), // right side
Math.sqrt( Math.pow(d2x-d3x, 2) + Math.pow(d2y-d3y, 2) ), // bottom side
Math.sqrt( Math.pow(d3x-d0x, 2) + Math.pow(d3y-d0y, 2) ) // left side
];
//
var ow = this.p.cvso.width;
var oh = this.p.cvso.height;
// specify the index of which dimension is longest
var base_index = 0;
var max_scale_rate = 0;
var zero_num = 0;
for( var i=0; i<4; i++ ) {
var rate = 0;
if( i % 2 ) {
rate = dims[i] / ow;
} else {
rate = dims[i] / oh;
}
if( rate > max_scale_rate ) {
base_index = i;
max_scale_rate = rate;
}
if( dims[i] == 0 ) {
zero_num ++;
}
}
if(zero_num > 1) { return; }
//
var step = 2;
var cover_step = step * 5;
//
var ctxo = this.p.ctxo;
var ctxt = this.p.ctxt;
ctxt.clearRect(0, 0, ctxt.canvas.width, ctxt.canvas.height);
if(base_index % 2 == 0) { // top or bottom side
var ctxl = this.create_canvas_context(ow, cover_step);
ctxl.globalCompositeOperation = "copy";
var cvsl = ctxl.canvas;
for( var y=0; y<oh; y+=step ) {
var r = y / oh;
var sx = d0x + (d3x-d0x) * r;
var sy = d0y + (d3y-d0y) * r;
var ex = d1x + (d2x-d1x) * r;
var ey = d1y + (d2y-d1y) * r;
var ag = Math.atan( (ey-sy) / (ex-sx) );
var sc = Math.sqrt( Math.pow(ex-sx, 2) + Math.pow(ey-sy, 2) ) / ow;
ctxl.setTransform(1, 0, 0, 1, 0, -y);
ctxl.drawImage(ctxo.canvas, 0, 0);
//
ctxt.translate(sx, sy);
ctxt.rotate(ag);
ctxt.scale(sc, sc);
ctxt.drawImage(cvsl, 0, 0);
//
ctxt.setTransform(1, 0, 0, 1, 0, 0);
}
} else if(base_index % 2 == 1) { // right or left side
var ctxl = this.create_canvas_context(cover_step, oh);
ctxl.globalCompositeOperation = "copy";
var cvsl = ctxl.canvas;
for( var x=0; x<ow; x+=step ) {
var r = x / ow;
var sx = d0x + (d1x-d0x) * r;
var sy = d0y + (d1y-d0y) * r;
var ex = d3x + (d2x-d3x) * r;
var ey = d3y + (d2y-d3y) * r;
var ag = Math.atan( (sx-ex) / (ey-sy) );
var sc = Math.sqrt( Math.pow(ex-sx, 2) + Math.pow(ey-sy, 2) ) / oh;
ctxl.setTransform(1, 0, 0, 1, -x, 0);
ctxl.drawImage(ctxo.canvas, 0, 0);
//
ctxt.translate(sx, sy);
ctxt.rotate(ag);
ctxt.scale(sc, sc);
ctxt.drawImage(cvsl, 0, 0);
//
ctxt.setTransform(1, 0, 0, 1, 0, 0);
}
}
// set a clipping path and draw the transformed image on the destination canvas.
this.p.ctxd.save();
this.p.ctxd.drawImage(ctxt.canvas, 0, 0);
this._applyMask(this.p.ctxd, [[d0x, d0y], [d1x, d1y], [d2x, d2y], [d3x, d3y]]);
this.p.ctxd.restore();
}
/* -------------------------------------------------------------------
* private methods
* ----------------------------------------------------------------- */
proto.create_canvas_context = function(w, h) {
var canvas = document.createElement('canvas');
canvas.width = w;
canvas.height = h;
var ctx = canvas.getContext('2d');
return ctx;
};
proto._applyMask = function(ctx, points) {
ctx.beginPath();
ctx.moveTo(points[0][0], points[0][1]);
for( var i=1; i<points.length; i++ ) {
ctx.lineTo(points[i][0], points[i][1]);
}
ctx.closePath();
ctx.globalCompositeOperation = "destination-in";
ctx.fill();
ctx.globalCompositeOperation = "source-over";
};
})();
module.exports = html5jp.perspective;
},{}]},{},[1])(1)
});
<!doctype html>
<html>
<head>
<title>Perspective.js demo</title>
</head>
<body>
<canvas id="canvas"></canvas>
<script>
var canvas = document.getElementById("canvas");
var image = new Image();
image.onload = function() {
canvas.width = image.width;
canvas.height = image.height;
var ctx = canvas.getContext("2d");
var p = new Perspective(ctx, image);
p.draw([
[50, 100],
[image.width - 20, 1],
[image.width - 10, image.height - 1],
[10, image.height]
]);
}
image.src = "https://i.stack.imgur.com/bt0xs.png";
</script>
</body>
</html>
