问题
I'm using this in my app:
http://www.html5canvastutorials.com/labs/html5-canvas-drag-and-drop-resize-and-invert-images/
have use anchors for resizing the image ..
What I want is to resize the image and keep its ratio maintained. I don't want it to stretch I'm able to achieve that using this peace of code.:..
if(width) {
image.setSize(width);
}
But this is screwing up the anchors .. Anyone ever tried something like this..
回答1:
I know this is a horribly old post but I needed to implement this exact thing and found the accepted answer is quite flawed - the left two drag handles move the entire image and act very much unlike an image editing program would, for instance. I am posting my solution in case someone stumbles upon this from a Google search like I did.
// Update the positions of handles during drag.
// This needs to happen so the dimension calculation can use the
// handle positions to determine the new width/height.
switch (activeHandleName) {
case "topLeft":
topRight.setY(activeHandle.getY());
bottomLeft.setX(activeHandle.getX());
break;
case "topRight":
topLeft.setY(activeHandle.getY());
bottomRight.setX(activeHandle.getX());
break;
case "bottomRight":
bottomLeft.setY(activeHandle.getY());
topRight.setX(activeHandle.getX());
break;
case "bottomLeft":
bottomRight.setY(activeHandle.getY());
topLeft.setX(activeHandle.getX());
break;
}
// Calculate new dimensions. Height is simply the dy of the handles.
// Width is increased/decreased by a factor of how much the height changed.
newHeight = bottomLeft.getY() - topLeft.getY();
newWidth = image.getWidth() * newHeight / image.getHeight();
// Move the image to adjust for the new dimensions.
// The position calculation changes depending on where it is anchored.
// ie. When dragging on the right, it is anchored to the top left,
// when dragging on the left, it is anchored to the top right.
if(activeHandleName === "topRight" || activeHandleName === "bottomRight") {
image.setPosition(topLeft.getX(), topLeft.getY());
} else if(activeHandleName === "topLeft" || activeHandleName === "bottomLeft") {
image.setPosition(topRight.getX() - newWidth, topRight.getY());
}
imageX = image.getX();
imageY = image.getY();
// Update handle positions to reflect new image dimensions
topLeft.setPosition(imageX, imageY);
topRight.setPosition(imageX + newWidth, imageY);
bottomRight.setPosition(imageX + newWidth, imageY + newHeight);
bottomLeft.setPosition(imageX, imageY + newHeight);
// Set the image's size to the newly calculated dimensions
if(newWidth && newHeight) {
image.setSize(newWidth, newHeight);
}
Modified KineticJS example in JSBin: http://jsbin.com/iyimuy/1/edit
回答2:
Change lines:
var width = topRight.attrs.x - topLeft.attrs.x;
var height = bottomLeft.attrs.y - topLeft.attrs.y;
if(width && height) {
image.setSize(width, height);
}
To:
var height = bottomLeft.attrs.y - topLeft.attrs.y;
var width = image.getWidth()*height/image.getHeight();
topRight.attrs.x = topLeft.attrs.x + width;
topRight.attrs.y = topLeft.attrs.y;
bottomRight.attrs.x = topLeft.attrs.x + width;
bottomRight.attrs.y = topLeft.attrs.y + height;
if(width && height) {
image.setSize(width, height);
}
Example
回答3:
Here it is: JSFIDDLE
JS:
function update(group, activeHandle) {
var topLeft = group.get(".topLeft")[0],
topRight = group.get(".topRight")[0],
bottomRight = group.get(".bottomRight")[0],
bottomLeft = group.get(".bottomLeft")[0],
image = group.get(".image")[0],
activeHandleName = activeHandle.getName(),
newWidth,
newHeight,
minWidth = 32,
minHeight = 32,
oldX,
oldY,
imageX,
imageY;
// Update the positions of handles during drag.
// This needs to happen so the dimension calculation can use the
// handle positions to determine the new width/height.
switch (activeHandleName) {
case "topLeft":
oldY = topRight.getY();
oldX = bottomLeft.getX();
topRight.setY(activeHandle.getY());
bottomLeft.setX(activeHandle.getX());
break;
case "topRight":
oldY = topLeft.getY();
oldX = bottomRight.getX();
topLeft.setY(activeHandle.getY());
bottomRight.setX(activeHandle.getX());
break;
case "bottomRight":
oldY = bottomLeft.getY();
oldX = topRight.getX();
bottomLeft.setY(activeHandle.getY());
topRight.setX(activeHandle.getX());
break;
case "bottomLeft":
oldY = bottomRight.getY();
oldX = topLeft.getX();
bottomRight.setY(activeHandle.getY());
topLeft.setX(activeHandle.getX());
break;
}
// Calculate new dimensions. Height is simply the dy of the handles.
// Width is increased/decreased by a factor of how much the height changed.
newHeight = bottomLeft.getY() - topLeft.getY();
newWidth = image.getWidth() * newHeight / image.getHeight();
// It's too small: move the active handle back to the old position
if( newWidth < minWidth || newHeight < minHeight ){
activeHandle.setY(oldY);
activeHandle.setX(oldX);
switch (activeHandleName) {
case "topLeft":
topRight.setY(oldY);
bottomLeft.setX(oldX);
break;
case "topRight":
topLeft.setY(oldY);
bottomRight.setX(oldX);
break;
case "bottomRight":
bottomLeft.setY(oldY);
topRight.setX(oldX);
break;
case "bottomLeft":
bottomRight.setY(oldY);
topLeft.setX(oldX);
break;
}
}
newHeight = bottomLeft.getY() - topLeft.getY();
//comment the below line and uncomment the line below tha line to allow free resize of the images because the below line preserves the scale and aspect ratio
newWidth = image.getWidth() * newHeight / image.getHeight();//for restricted resizing
//newWidth = topRight.getX() - topLeft.getX();//for free resizing
// Move the image to adjust for the new dimensions.
// The position calculation changes depending on where it is anchored.
// ie. When dragging on the right, it is anchored to the top left,
// when dragging on the left, it is anchored to the top right.
if(activeHandleName === "topRight" || activeHandleName === "bottomRight") {
image.setPosition(topLeft.getX(), topLeft.getY());
} else if(activeHandleName === "topLeft" || activeHandleName === "bottomLeft") {
image.setPosition(topRight.getX() - newWidth, topRight.getY());
}
imageX = image.getX();
imageY = image.getY();
// Update handle positions to reflect new image dimensions
topLeft.setPosition(imageX, imageY);
topRight.setPosition(imageX + newWidth, imageY);
bottomRight.setPosition(imageX + newWidth, imageY + newHeight);
bottomLeft.setPosition(imageX, imageY + newHeight);
// Set the image's size to the newly calculated dimensions
if(newWidth && newHeight) {
image.setSize(newWidth, newHeight);
}
}
function addAnchor(group, x, y, name) {
var stage = group.getStage();
var layer = group.getLayer();
var anchor = new Kinetic.Circle({
x: x,
y: y,
stroke: "#666",
fill: "#ddd",
strokeWidth: 2,
radius: 8,
name: name,
draggable: true
});
anchor.on("dragmove", function() {
update(group, this);
layer.draw();
});
anchor.on("mousedown touchstart", function() {
group.setDraggable(false);
this.moveToTop();
});
anchor.on("dragend", function() {
group.setDraggable(true);
layer.draw();
});
// add hover styling
anchor.on("mouseover", function() {
var layer = this.getLayer();
document.body.style.cursor = "pointer";
this.setStrokeWidth(4);
layer.draw();
});
anchor.on("mouseout", function() {
var layer = this.getLayer();
document.body.style.cursor = "default";
this.setStrokeWidth(2);
layer.draw();
});
group.add(anchor);
}
function loadImages(sources, callback) {
var images = {};
var loadedImages = 0;
var numImages = 0;
for(var src in sources) {
numImages++;
}
for(var src in sources) {
images[src] = new Image();
images[src].onload = function() {
if(++loadedImages >= numImages) {
callback(images);
}
};
images[src].src = sources[src];
}
}
function initStage(images) {
var stage = new Kinetic.Stage({
container: "container",
width: 578,
height: 400
});
var darthVaderGroup = new Kinetic.Group({
x: 270,
y: 100,
draggable: true
});
var yodaGroup = new Kinetic.Group({
x: 100,
y: 110,
draggable: true
});
var layer = new Kinetic.Layer();
/*
* go ahead and add the groups
* to the layer and the layer to the
* stage so that the groups have knowledge
* of its layer and stage
*/
layer.add(darthVaderGroup);
layer.add(yodaGroup);
stage.add(layer);
// darth vader
var darthVaderImg = new Kinetic.Image({
x: 0,
y: 0,
image: images.darthVader,
width: 200,
height: 138,
name: "image"
});
darthVaderGroup.add(darthVaderImg);
addAnchor(darthVaderGroup, 0, 0, "topLeft");
addAnchor(darthVaderGroup, 200, 0, "topRight");
addAnchor(darthVaderGroup, 200, 138, "bottomRight");
addAnchor(darthVaderGroup, 0, 138, "bottomLeft");
darthVaderGroup.on("dragstart", function() {
this.moveToTop();
});
// yoda
var yodaImg = new Kinetic.Image({
x: 0,
y: 0,
image: images.yoda,
width: 93,
height: 104,
name: "image"
});
yodaGroup.add(yodaImg);
addAnchor(yodaGroup, 0, 0, "topLeft");
addAnchor(yodaGroup, 93, 0, "topRight");
addAnchor(yodaGroup, 93, 104, "bottomRight");
addAnchor(yodaGroup, 0, 104, "bottomLeft");
yodaGroup.on("dragstart", function() {
this.moveToTop();
});
stage.draw();
}
var sources = {
darthVader: 'http://www.html5canvastutorials.com/demos/assets/darth-vader.jpg',
yoda: 'http://www.html5canvastutorials.com/demos/assets/yoda.jpg'
};
loadImages(sources, initStage);
回答4:
I know is not the question but Ive lost a lot of time trying to solve the problem when the anchors go beyond the image 0 size, which throws a javasacript error:
IndexSizeError: Index or size is negative or greater than the allowed amount
What I did is adding Math.abs to the image size calcuation formula :
newHeight = Math.abs(bottomLeft.getY() - topLeft.getY());
newWidth = Math.abs(image.getWidth() * newHeight / image.getHeight());
It works fine with both bottom anchors, but not so well with top anchors, I just removed the top anchors which is good enough solution for my project....
Hope this helps someone!
来源：https://stackoverflow.com/questions/13139671/resizing-the-images-while-keeping-proportion-using-kinetic-js-canvas