[英]Draw distorted image on html5's canvas
是否有可能,如果可以,如何繪制四個角扭曲成非矩形的圖像。 例如,如果您想要繪制圖像,就好像它在 3d 空間中旋轉了一樣。
我基於 Thatcher Ulrich 的代碼 ( http://tulrich.com/geekstuff/canvas/perspective.html ) 創建了一個簡單的 4 點變換。 這個版本只是提取了一小部分三角形代碼並處理幾何細分以進行適當的轉換。 享受!
http://jsfiddle.net/mrbendel/6rbtde5t/1/
var controls = [];
var canvas;
var context;
var image;
var triangles = [];
var dirtyTriangles = true;
var rand = function(s,e) {
return Math.random() * (e-s) + s;
}
// dom ready
$(document).ready(function() {
image = new Image();
$(image).load(function() {
setInterval(draw, 1000 / 60);
});
$(image).attr('src', 'http://media.giphy.com/media/NWb6sWXQQTqwg/giphy.gif');
canvas = document.createElement('canvas');
$(canvas).attr('width', 500);
$(canvas).attr('height', 500);
$('body').append(canvas);
context = canvas.getContext('2d');
//
for (var i = 0; i < 4; ++i) {
var control = document.createElement('div');
$(control).addClass('node');
$('body').append(control);
controls.push(control);
}
$(controls[0]).css('left', rand(25, 225));
$(controls[0]).css('top', rand(25, 225));
$(controls[1]).css('left', rand(250, 475));
$(controls[1]).css('top', rand(25, 225));
$(controls[2]).css('left', rand(250, 475));
$(controls[2]).css('top', rand(250, 475));
$(controls[3]).css('left', rand(25, 225));
$(controls[3]).css('top', rand(250, 475));
$('body').mousedown(function(e) {
if ($(e.target).hasClass('node')) {
var node = e.target;
$('body').mousemove(function(e) {
var x = e.pageX;
var y = e.pageY;
$(node).css('left', x);
$(node).css('top', y);
dirtyTriangles = true;
});
$('body').mouseup(function(e) {
$('body').off( "mousemove" );
$('body').off( "mouseup" );
});
}
});
});
var draw = function() {
context.clearRect(0,0,500,500);
var render = function(wireframe, image, tri) {
if (wireframe) {
context.strokeStyle = "black";
context.beginPath();
context.moveTo(tri.p0.x, tri.p0.y);
context.lineTo(tri.p1.x, tri.p1.y);
context.lineTo(tri.p2.x, tri.p2.y);
context.lineTo(tri.p0.x, tri.p0.y);
context.stroke();
context.closePath();
}
if (image) {
drawTriangle(context, image,
tri.p0.x, tri.p0.y,
tri.p1.x, tri.p1.y,
tri.p2.x, tri.p2.y,
tri.t0.u, tri.t0.v,
tri.t1.u, tri.t1.v,
tri.t2.u, tri.t2.v);
}
}
if (dirtyTriangles) {
dirtyTriangles = false;
calculateGeometry();
}
for (triangle of triangles) {
render(true, image, triangle);
}
}
var calculateGeometry = function() {
// clear triangles out
triangles = [];
// generate subdivision
var subs = 7; // vertical subdivisions
var divs = 7; // horizontal subdivisions
var p1 = new Point(parseInt($(controls[0]).css('left')) + 6, parseInt($(controls[0]).css('top')) + 6);
var p2 = new Point(parseInt($(controls[1]).css('left')) + 6, parseInt($(controls[1]).css('top')) + 6);
var p3 = new Point(parseInt($(controls[2]).css('left')) + 6, parseInt($(controls[2]).css('top')) + 6);
var p4 = new Point(parseInt($(controls[3]).css('left')) + 6, parseInt($(controls[3]).css('top')) + 6);
var dx1 = p4.x - p1.x;
var dy1 = p4.y - p1.y;
var dx2 = p3.x - p2.x;
var dy2 = p3.y - p2.y;
var imgW = image.naturalWidth;
var imgH = image.naturalHeight;
for (var sub = 0; sub < subs; ++sub) {
var curRow = sub / subs;
var nextRow = (sub + 1) / subs;
var curRowX1 = p1.x + dx1 * curRow;
var curRowY1 = p1.y + dy1 * curRow;
var curRowX2 = p2.x + dx2 * curRow;
var curRowY2 = p2.y + dy2 * curRow;
var nextRowX1 = p1.x + dx1 * nextRow;
var nextRowY1 = p1.y + dy1 * nextRow;
var nextRowX2 = p2.x + dx2 * nextRow;
var nextRowY2 = p2.y + dy2 * nextRow;
for (var div = 0; div < divs; ++div) {
var curCol = div / divs;
var nextCol = (div + 1) / divs;
var dCurX = curRowX2 - curRowX1;
var dCurY = curRowY2 - curRowY1;
var dNextX = nextRowX2 - nextRowX1;
var dNextY = nextRowY2 - nextRowY1;
var p1x = curRowX1 + dCurX * curCol;
var p1y = curRowY1 + dCurY * curCol;
var p2x = curRowX1 + (curRowX2 - curRowX1) * nextCol;
var p2y = curRowY1 + (curRowY2 - curRowY1) * nextCol;
var p3x = nextRowX1 + dNextX * nextCol;
var p3y = nextRowY1 + dNextY * nextCol;
var p4x = nextRowX1 + dNextX * curCol;
var p4y = nextRowY1 + dNextY * curCol;
var u1 = curCol * imgW;
var u2 = nextCol * imgW;
var v1 = curRow * imgH;
var v2 = nextRow * imgH;
var triangle1 = new Triangle(
new Point(p1x, p1y),
new Point(p3x, p3y),
new Point(p4x, p4y),
new TextCoord(u1, v1),
new TextCoord(u2, v2),
new TextCoord(u1, v2)
);
var triangle2 = new Triangle(
new Point(p1x, p1y),
new Point(p2x, p2y),
new Point(p3x, p3y),
new TextCoord(u1, v1),
new TextCoord(u2, v1),
new TextCoord(u2, v2)
);
triangles.push(triangle1);
triangles.push(triangle2);
}
}
}
// from http://tulrich.com/geekstuff/canvas/jsgl.js
var drawTriangle = function(ctx, im, x0, y0, x1, y1, x2, y2,
sx0, sy0, sx1, sy1, sx2, sy2) {
ctx.save();
// Clip the output to the on-screen triangle boundaries.
ctx.beginPath();
ctx.moveTo(x0, y0);
ctx.lineTo(x1, y1);
ctx.lineTo(x2, y2);
ctx.closePath();
//ctx.stroke();//xxxxxxx for wireframe
ctx.clip();
/*
ctx.transform(m11, m12, m21, m22, dx, dy) sets the context transform matrix.
The context matrix is:
[ m11 m21 dx ]
[ m12 m22 dy ]
[ 0 0 1 ]
Coords are column vectors with a 1 in the z coord, so the transform is:
x_out = m11 * x + m21 * y + dx;
y_out = m12 * x + m22 * y + dy;
From Maxima, these are the transform values that map the source
coords to the dest coords:
sy0 (x2 - x1) - sy1 x2 + sy2 x1 + (sy1 - sy2) x0
[m11 = - -----------------------------------------------------,
sx0 (sy2 - sy1) - sx1 sy2 + sx2 sy1 + (sx1 - sx2) sy0
sy1 y2 + sy0 (y1 - y2) - sy2 y1 + (sy2 - sy1) y0
m12 = -----------------------------------------------------,
sx0 (sy2 - sy1) - sx1 sy2 + sx2 sy1 + (sx1 - sx2) sy0
sx0 (x2 - x1) - sx1 x2 + sx2 x1 + (sx1 - sx2) x0
m21 = -----------------------------------------------------,
sx0 (sy2 - sy1) - sx1 sy2 + sx2 sy1 + (sx1 - sx2) sy0
sx1 y2 + sx0 (y1 - y2) - sx2 y1 + (sx2 - sx1) y0
m22 = - -----------------------------------------------------,
sx0 (sy2 - sy1) - sx1 sy2 + sx2 sy1 + (sx1 - sx2) sy0
sx0 (sy2 x1 - sy1 x2) + sy0 (sx1 x2 - sx2 x1) + (sx2 sy1 - sx1 sy2) x0
dx = ----------------------------------------------------------------------,
sx0 (sy2 - sy1) - sx1 sy2 + sx2 sy1 + (sx1 - sx2) sy0
sx0 (sy2 y1 - sy1 y2) + sy0 (sx1 y2 - sx2 y1) + (sx2 sy1 - sx1 sy2) y0
dy = ----------------------------------------------------------------------]
sx0 (sy2 - sy1) - sx1 sy2 + sx2 sy1 + (sx1 - sx2) sy0
*/
// TODO: eliminate common subexpressions.
var denom = sx0 * (sy2 - sy1) - sx1 * sy2 + sx2 * sy1 + (sx1 - sx2) * sy0;
if (denom == 0) {
return;
}
var m11 = -(sy0 * (x2 - x1) - sy1 * x2 + sy2 * x1 + (sy1 - sy2) * x0) / denom;
var m12 = (sy1 * y2 + sy0 * (y1 - y2) - sy2 * y1 + (sy2 - sy1) * y0) / denom;
var m21 = (sx0 * (x2 - x1) - sx1 * x2 + sx2 * x1 + (sx1 - sx2) * x0) / denom;
var m22 = -(sx1 * y2 + sx0 * (y1 - y2) - sx2 * y1 + (sx2 - sx1) * y0) / denom;
var dx = (sx0 * (sy2 * x1 - sy1 * x2) + sy0 * (sx1 * x2 - sx2 * x1) + (sx2 * sy1 - sx1 * sy2) * x0) / denom;
var dy = (sx0 * (sy2 * y1 - sy1 * y2) + sy0 * (sx1 * y2 - sx2 * y1) + (sx2 * sy1 - sx1 * sy2) * y0) / denom;
ctx.transform(m11, m12, m21, m22, dx, dy);
// Draw the whole image. Transform and clip will map it onto the
// correct output triangle.
//
// TODO: figure out if drawImage goes faster if we specify the rectangle that
// bounds the source coords.
ctx.drawImage(im, 0, 0);
ctx.restore();
};
// point class
var Point = function(x,y) {
this.x = x?x:0;
this.y = y?y:0;
}
var p = Point.prototype;
p.length = function(point) {
point = point?point:new Point();
var xs =0, ys =0;
xs = point.x - this.x;
xs = xs * xs;
ys = point.y - this.y;
ys = ys * ys;
return Math.sqrt( xs + ys );
}
var TextCoord = function(u,v) {
this.u = u?u:0;
this.v = v?v:0;
}
var Triangle = function(p0, p1, p2, t0, t1, t2) {
this.p0 = p0;
this.p1 = p1;
this.p2 = p2;
this.t0 = t0;
this.t1 = t1;
this.t2 = t2;
}
最簡單的方法是在繪制圖像之前對畫布應用轉換。
http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#transformations
通過傾斜變換,您可以使它看起來像透視圖
這是一個非常簡單的例子:
ctx.setTransform (1, -0.2, 0, 1, 0, 0);
ctx.drawImage(blah);
您可以嘗試此處說明的function transferPoint (xI, yI, source, destination)
。
源和目標是源和目標矩形的四個點。 該代碼適用於(SVG)路徑坐標(曲線和線),但經過一些修改后也適用於像素。
上面的一些評論者詢問了隱藏三角形 - 這樣做,它們會消失(信息:@erbridge,@Constantin Groß):
以下所有功勞仍然歸功於@AndyPoes,因為這是他的全部建議 - 我只是添加了他建議的完整版本。
改變這一行:
render(true, image, triangle);
對此:
render(false, image, triangle);
...黑色三角形將消失,但您會看到三角形之間的間隙,所以現在執行以下操作:
改變這個:
var triangle1 = new Triangle(
new Point(p1x, p1y),
new Point(p3x, p3y),
new Point(p4x, p4y),
new TextCoord(u1, v1),
new TextCoord(u2, v2),
new TextCoord(u1, v2)
);
var triangle2 = new Triangle(
new Point(p1x, p1y),
new Point(p2x, p2y),
new Point(p3x, p3y),
new TextCoord(u1, v1),
new TextCoord(u2, v1),
new TextCoord(u2, v2)
);
對此:
var triangle1 = new Triangle(
new Point(p1x-1, p1y),
new Point(p3x+2, p3y+1),
new Point(p4x-1, p4y+1),
new TextCoord(u1, v1),
new TextCoord(u2, v2),
new TextCoord(u1, v2)
);
var triangle2 = new Triangle(
new Point(p1x-2, p1y),
new Point(p2x+1, p2y),
new Point(p3x+1, p3y+1),
new TextCoord(u1, v1),
new TextCoord(u2, v1),
new TextCoord(u2, v2)
);
....並且差距將被關閉。
新小提琴 =屋頂上的小提琴手
完整代碼在這里:
var controls = [];
var canvas;
var context;
var image;
var triangles = [];
var dirtyTriangles = false;
var rand = function(s,e) {
return Math.random() * (e-s) + s;
}
// dom ready
$(document).ready(function() {
image = new Image();
$(image).load(function() {
setInterval(draw, 1000 / 60);
});
$(image).attr('src', 'https://images.unsplash.com/photo-1500964757637-c85e8a162699?ixlib=rb-1.2.1&q=80&fm=jpg');
canvas = document.createElement('canvas');
$(canvas).attr('width', 500);
$(canvas).attr('height', 500);
$('body').append(canvas);
context = canvas.getContext('2d');
//
for (var i = 0; i < 4; ++i) {
var control = document.createElement('div');
$(control).addClass('node');
$('body').append(control);
controls.push(control);
}
$(controls[0]).css('left', rand(25, 225));
$(controls[0]).css('top', rand(25, 225));
$(controls[1]).css('left', rand(250, 475));
$(controls[1]).css('top', rand(25, 225));
$(controls[2]).css('left', rand(250, 475));
$(controls[2]).css('top', rand(250, 475));
$(controls[3]).css('left', rand(25, 225));
$(controls[3]).css('top', rand(250, 475));
$('body').mousedown(function(e) {
if ($(e.target).hasClass('node')) {
var node = e.target;
$('body').mousemove(function(e) {
var x = e.pageX;
var y = e.pageY;
$(node).css('left', x);
$(node).css('top', y);
dirtyTriangles = true;
});
$('body').mouseup(function(e) {
$('body').off( "mousemove" );
$('body').off( "mouseup" );
});
}
});
});
var draw = function() {
context.clearRect(0,0,500,500);
var render = function(wireframe, image, tri) {
if (wireframe) {
context.strokeStyle = "black";
context.beginPath();
context.moveTo(tri.p0.x, tri.p0.y);
context.lineTo(tri.p1.x, tri.p1.y);
context.lineTo(tri.p2.x, tri.p2.y);
context.lineTo(tri.p0.x, tri.p0.y);
context.stroke();
context.closePath();
}
if (image) {
drawTriangle(context, image,
tri.p0.x, tri.p0.y,
tri.p1.x, tri.p1.y,
tri.p2.x, tri.p2.y,
tri.t0.u, tri.t0.v,
tri.t1.u, tri.t1.v,
tri.t2.u, tri.t2.v);
}
}
if (dirtyTriangles) {
dirtyTriangles = false;
calculateGeometry();
}
for (triangle of triangles) {
render(true, image, triangle);
}
}
var calculateGeometry = function() {
// clear triangles out
triangles = [];
// generate subdivision
var subs = 7; // vertical subdivisions
var divs = 7; // horizontal subdivisions
var p1 = new Point(parseInt($(controls[0]).css('left')) + 6, parseInt($(controls[0]).css('top')) + 6);
var p2 = new Point(parseInt($(controls[1]).css('left')) + 6, parseInt($(controls[1]).css('top')) + 6);
var p3 = new Point(parseInt($(controls[2]).css('left')) + 6, parseInt($(controls[2]).css('top')) + 6);
var p4 = new Point(parseInt($(controls[3]).css('left')) + 6, parseInt($(controls[3]).css('top')) + 6);
var dx1 = p4.x - p1.x;
var dy1 = p4.y - p1.y;
var dx2 = p3.x - p2.x;
var dy2 = p3.y - p2.y;
var imgW = image.naturalWidth;
var imgH = image.naturalHeight;
for (var sub = 0; sub < subs; ++sub) {
var curRow = sub / subs;
var nextRow = (sub + 1) / subs;
var curRowX1 = p1.x + dx1 * curRow;
var curRowY1 = p1.y + dy1 * curRow;
var curRowX2 = p2.x + dx2 * curRow;
var curRowY2 = p2.y + dy2 * curRow;
var nextRowX1 = p1.x + dx1 * nextRow;
var nextRowY1 = p1.y + dy1 * nextRow;
var nextRowX2 = p2.x + dx2 * nextRow;
var nextRowY2 = p2.y + dy2 * nextRow;
for (var div = 0; div < divs; ++div) {
var curCol = div / divs;
var nextCol = (div + 1) / divs;
var dCurX = curRowX2 - curRowX1;
var dCurY = curRowY2 - curRowY1;
var dNextX = nextRowX2 - nextRowX1;
var dNextY = nextRowY2 - nextRowY1;
var p1x = curRowX1 + dCurX * curCol;
var p1y = curRowY1 + dCurY * curCol;
var p2x = curRowX1 + (curRowX2 - curRowX1) * nextCol;
var p2y = curRowY1 + (curRowY2 - curRowY1) * nextCol;
var p3x = nextRowX1 + dNextX * nextCol;
var p3y = nextRowY1 + dNextY * nextCol;
var p4x = nextRowX1 + dNextX * curCol;
var p4y = nextRowY1 + dNextY * curCol;
var u1 = curCol * imgW;
var u2 = nextCol * imgW;
var v1 = curRow * imgH;
var v2 = nextRow * imgH;
var triangle1 = new Triangle(
new Point(p1x-1, p1y),
new Point(p3x+2, p3y+1),
new Point(p4x-1, p4y+1),
new TextCoord(u1, v1),
new TextCoord(u2, v2),
new TextCoord(u1, v2)
);
var triangle2 = new Triangle(
new Point(p1x-2, p1y),
new Point(p2x+1, p2y),
new Point(p3x+1, p3y+1),
new TextCoord(u1, v1),
new TextCoord(u2, v1),
new TextCoord(u2, v2)
);
triangles.push(triangle1);
triangles.push(triangle2);
}
}
}
// from http://tulrich.com/geekstuff/canvas/jsgl.js
var drawTriangle = function(ctx, im, x0, y0, x1, y1, x2, y2,
sx0, sy0, sx1, sy1, sx2, sy2) {
ctx.save();
// Clip the output to the on-screen triangle boundaries.
ctx.beginPath();
ctx.moveTo(x0, y0);
ctx.lineTo(x1, y1);
ctx.lineTo(x2, y2);
ctx.closePath();
//ctx.stroke();//xxxxxxx for wireframe
ctx.clip();
/*
ctx.transform(m11, m12, m21, m22, dx, dy) sets the context transform matrix.
The context matrix is:
[ m11 m21 dx ]
[ m12 m22 dy ]
[ 0 0 1 ]
Coords are column vectors with a 1 in the z coord, so the transform is:
x_out = m11 * x + m21 * y + dx;
y_out = m12 * x + m22 * y + dy;
From Maxima, these are the transform values that map the source
coords to the dest coords:
sy0 (x2 - x1) - sy1 x2 + sy2 x1 + (sy1 - sy2) x0
[m11 = - -----------------------------------------------------,
sx0 (sy2 - sy1) - sx1 sy2 + sx2 sy1 + (sx1 - sx2) sy0
sy1 y2 + sy0 (y1 - y2) - sy2 y1 + (sy2 - sy1) y0
m12 = -----------------------------------------------------,
sx0 (sy2 - sy1) - sx1 sy2 + sx2 sy1 + (sx1 - sx2) sy0
sx0 (x2 - x1) - sx1 x2 + sx2 x1 + (sx1 - sx2) x0
m21 = -----------------------------------------------------,
sx0 (sy2 - sy1) - sx1 sy2 + sx2 sy1 + (sx1 - sx2) sy0
sx1 y2 + sx0 (y1 - y2) - sx2 y1 + (sx2 - sx1) y0
m22 = - -----------------------------------------------------,
sx0 (sy2 - sy1) - sx1 sy2 + sx2 sy1 + (sx1 - sx2) sy0
sx0 (sy2 x1 - sy1 x2) + sy0 (sx1 x2 - sx2 x1) + (sx2 sy1 - sx1 sy2) x0
dx = ----------------------------------------------------------------------,
sx0 (sy2 - sy1) - sx1 sy2 + sx2 sy1 + (sx1 - sx2) sy0
sx0 (sy2 y1 - sy1 y2) + sy0 (sx1 y2 - sx2 y1) + (sx2 sy1 - sx1 sy2) y0
dy = ----------------------------------------------------------------------]
sx0 (sy2 - sy1) - sx1 sy2 + sx2 sy1 + (sx1 - sx2) sy0
*/
// TODO: eliminate common subexpressions.
var denom = sx0 * (sy2 - sy1) - sx1 * sy2 + sx2 * sy1 + (sx1 - sx2) * sy0;
if (denom == 0) {
return;
}
var m11 = -(sy0 * (x2 - x1) - sy1 * x2 + sy2 * x1 + (sy1 - sy2) * x0) / denom;
var m12 = (sy1 * y2 + sy0 * (y1 - y2) - sy2 * y1 + (sy2 - sy1) * y0) / denom;
var m21 = (sx0 * (x2 - x1) - sx1 * x2 + sx2 * x1 + (sx1 - sx2) * x0) / denom;
var m22 = -(sx1 * y2 + sx0 * (y1 - y2) - sx2 * y1 + (sx2 - sx1) * y0) / denom;
var dx = (sx0 * (sy2 * x1 - sy1 * x2) + sy0 * (sx1 * x2 - sx2 * x1) + (sx2 * sy1 - sx1 * sy2) * x0) / denom;
var dy = (sx0 * (sy2 * y1 - sy1 * y2) + sy0 * (sx1 * y2 - sx2 * y1) + (sx2 * sy1 - sx1 * sy2) * y0) / denom;
ctx.transform(m11, m12, m21, m22, dx, dy);
// Draw the whole image. Transform and clip will map it onto the
// correct output triangle.
//
// TODO: figure out if drawImage goes faster if we specify the rectangle that
// bounds the source coords.
ctx.drawImage(im, 0, 0);
ctx.restore();
};
// point class
var Point = function(x,y) {
this.x = x?x:0;
this.y = y?y:0;
}
var p = Point.prototype;
p.length = function(point) {
point = point?point:new Point();
var xs =0, ys =0;
xs = point.x - this.x;
xs = xs * xs;
ys = point.y - this.y;
ys = ys * ys;
return Math.sqrt( xs + ys );
}
var TextCoord = function(u,v) {
this.u = u?u:0;
this.v = v?v:0;
}
var Triangle = function(p0, p1, p2, t0, t1, t2) {
this.p0 = p0;
this.p1 = p1;
this.p2 = p2;
this.t0 = t0;
this.t1 = t1;
this.t2 = t2;
}
@Steve ,我注意到在您更新的 Fiddle 中第一次渲染時圖像是不可見的。 但是,一旦您開始與角落互動,它就會出現。 見下文
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