[英]canvas rotate isn't working as expected
http://jsfiddle.net/s1n6cssa/12/
的HTML
<a href="#" id="rotate">Rotate</a>
<div id="print-region">
<img class="overlay" src="http://www.itasveer.com/common/images/mobilecover/apple-5_5s.png" /> <span id="uploaded-image-container"></span>
<img class="overlay" src="http://www.itasveer.com/common/images/mobilecover/apple-5_5s_white.png" />
</div>
的CSS
#myCanvas {
height: 100%;
width: 100%;
background-color: blue;
}
#print-region {
height: 542px;
width: 520px;
margin: 0;
position: relative;
overflow: hidden;
}
.overlay {
position: absolute;
pointer-events: none;
}
#rotate {
width: 100px;
height: 30px;
}
JAVASCRIPT
var context;
var canvas;
var nHeight; //the new height after resizing
var nWidth; //the new width after resizing
var TO_RADIANS = Math.PI / 180;
var imageObj = new Image();
//USE ONLY ONE OF THE BELOW IMAGES AT A TIME
//square image which does not distort after rotation
imageObj.src = "http://i.stack.imgur.com/hwxO6.png";
//rectangular image which distorts after rotation
<!-- imageObj.src = "http://g-ecx.images-amazon.com/images/G/01/electronics/detail-page/Klipsch-Image-S4-II-Black-Lifestyle.jpg"; -->
var originalWidth = imageObj.width;
var originalHeight = imageObj.height;
$('#myCanvas').remove();
//used by context.rotate and updated after every rotation
$("#uploaded-image-container").attr({
rotation: 0
});
$("#uploaded-image-container").append("<canvas id='myCanvas'></canvas>");
$("#uploaded-image-container").css({
"position": "absolute",
"height": originalHeight / 3, //one-third size of the original height of the uploaded image
"width": originalWidth / 3,
"top": $('#print-region').height() / 3,
"left": $('#print-region').width() / 3
});
canvas = document.getElementById('myCanvas');
context = canvas.getContext('2d');
nHeight = canvas.height = originalHeight / 3;
nWidth = canvas.width = originalWidth / 3;
imageObj.onload = function () {
context.drawImage(imageObj, 0, 0, originalWidth / 3, originalHeight / 3);
};
$("#uploaded-image-container").draggable({
snap: false,
scroll: false,
cursor: "move",
containment: '#print-region'
});
$("#uploaded-image-container").resizable({
handles: 'nw, ne, sw, se',
aspectRatio: true,
containment: '#print-region',
resize: function (e, ui) {
nHeight = ui.size.height;
nWidth = ui.size.width;
}
});
$("#rotate").click(function () {
updateRotation($("#uploaded-image-container"));
});
var imageRotation = 0; // the angle that the image is rotated
var updateRotation = function (elem) {
var angle = parseInt(elem.attr('rotation'));
//after rotation, the nWidth and nHeight are interchanged hence temp variables
var tempHeight, tempWidth;
if (angle == 0) {
imageRotation = 90;
elem.attr('rotation', 90);
tempHeight = nWidth;
tempWidth = nHeight;
} else if (angle == 90) {
imageRotation = 180;
elem.attr('rotation', 180);
tempHeight = nHeight;
tempWidth = nWidth;
} else if (angle == 180) {
imageRotation = 270;
elem.attr('rotation', 270);
tempHeight = nWidth;
tempWidth = nHeight;
} else {
imageRotation = 0;
elem.attr('rotation', 0);
tempHeight = nHeight;
tempWidth = nWidth;
}
$("#uploaded-image-container").css({
"height": tempHeight,
"width": tempWidth
});
canvas.width = tempWidth;
canvas.height = tempHeight;
context.translate(tempWidth / 2, tempHeight / 2);
context.rotate(imageRotation * TO_RADIANS);
context.translate(-tempWidth / 2, -tempHeight / 2);
context.drawImage(imageObj, 0, 0, tempWidth, tempHeight);
};
我想使用html2canvas插件對jsfiddle結果中顯示的部分進行快照。 但是html2canvas不支持CSS3旋轉屬性。 因此,我使用canvas旋轉圖像,並且html2canvas成功捕獲了旋轉。
在上面的代碼中,當我使用正方形圖像時,它可以完美旋轉,但是當考慮矩形圖像時,圖像的寬度和高度會失真。
調整大小,拖動和旋轉的任何組合都不應使圖像變形。
有什么問題
試試這個http://jsfiddle.net/5hrx77nr/小提琴。
context.drawImage(imageObj, 0, 0, 100, 100 * imageObj.height / imageObj.width)
默認情況下,html5將圖像縮放到畫布大小,因此您必須手動管理圖像大小。
您應該多解釋一些您要做什么。 我認為輪換並不復雜
無論如何。 我在第33、34行發現了一個錯誤
nHeight = canvas.height = originalHeight / 3;
nWidth = canvas.width = originalWidth / 3;
也許您的意思是加法或乘法? 因為出現藍色畫布並在更改后旋轉。
nHeight = canvas.height + originalHeight / 3;
nWidth = canvas.width + originalWidth / 3;
這是因為在繪制和縮放圖像時使用臨時值(寬度和高度)作為方向。 然后將方向的值應用於setContainerHeight和setContainerWidth; 簡而言之:您使用與坐標和比例相同的值
我看不到您的第一張圖片(該圖片在我的國家被屏蔽),可能是因為它是正方形(寬=高); 因此沒有問題,但矩形的寬度= 2 *高度 ; 因此使用圖像比例。 這可以在任何盒子形狀中工作
var context;
var canvas;
var nHeight;
var nWidth;
var TO_RADIANS = Math.PI / 180;
var imageObj = new Image();
imageObj.src = "http://g-ecx.images-amazon.com/images/G/01/electronics/detail-page/Klipsch-Image-S4-II-Black-Lifestyle.jpg";
var originalWidth = imageObj.width;
var originalHeight = imageObj.height;
$('#myCanvas').remove();
$("#uploaded-image-container").attr({
rotation: 0
});
$("#uploaded-image-container").append("<canvas id='myCanvas'></canvas>");
$("#uploaded-image-container").css({
"position": "absolute",
"height": originalHeight / 3,
"width": originalWidth / 3,
"top": $('#print-region').height() / 3,
"left": $('#print-region').width() / 3
});
canvas = document.getElementById('myCanvas');
context = canvas.getContext('2d');
nHeight = canvas.height ;
nWidth = canvas.width ;
imageObj.onload = function () {
context.drawImage(imageObj, 0, 0, originalWidth / 3, originalHeight / 3);
};
$("#uploaded-image-container").draggable({
snap: false,
scroll: false,
cursor: "move",
containment: '#print-region'
});
$("#uploaded-image-container").resizable({
handles: 'nw, ne, sw, se',
aspectRatio: true,
containment: '#print-region',
resize: function (e, ui) {
nHeight = ui.size.height;
nWidth = ui.size.width;
}
});
$("#rotate").click(function () {
updateRotation($("#uploaded-image-container"));
});
var imageRotation = 0; // the angle that the image is rotated
var updateRotation = function (elem) {
var angle = parseInt(elem.attr('rotation'));
var ratio = nWidth/nHeight;
var customX = nWidth, scaleX = nWidth;
var customY = nHeight, scaleY = nHeight;
var tempHeight, tempWidth;
//the problem is in number 1 and 3
if (angle == 0) { //number 1
imageRotation = 90;
elem.attr('rotation', 90);
tempHeight = nWidth;
tempWidth = nHeight; customY = ratio*customY;
} else if (angle == 90) { //number 2
imageRotation = 180;
elem.attr('rotation', 180);
tempHeight = nHeight;
tempWidth = nWidth ;
} else if (angle == 180) {
imageRotation = 270;
elem.attr('rotation', 270);
tempHeight = nWidth;
tempWidth = nHeight; customY = ratio*customY;
} else { // number 4 handle
imageRotation = 0;
elem.attr('rotation', 0);
tempHeight = nHeight;
tempWidth = nWidth;
}
$("#uploaded-image-container").css({
"height": tempHeight,
"width": tempWidth
});
canvas.width = customX;
canvas.height = customY;
context.translate(customX / 2, customY / 2);
context.rotate(imageRotation * TO_RADIANS);
context.translate( -customX / 2, -customY / 2);
context.drawImage(imageObj, 0, 0, customX, customY);
};
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