作者:又未命名 | 来源:互联网 | 2023-05-25 20:18
我使用下面的代码在画布内绘制和缩放图像.问题是内部渲染的图像被拉伸以适应.
如果可能的话,我希望它根据宽度进行缩放,但要保持其宽高比.
有任何想法吗?
//IMAGE LOADER
var canvas = document.getElementById('image-canvas');
var canvas2 = document.getElementById('image-canvas2');
ctx = canvas.getContext('2d');
ctx2 = canvas2.getContext('2d');
// Trigger the imageLoader function when a file has been selected
var fileInput = document.getElementById('fileInput');
fileInput.addEventListener('change', imageLoader, false);
function imageLoader() {
var reader = new FileReader();
reader.Onload= function(event) {
img = new Image();
img.Onload= function(){
ctx.drawImage(img,0,0,canvas.width, canvas.height);
ctx2.drawImage(img,0,0,canvas.width, canvas.height);
}
img.src = reader.result;
}
reader.readAsDataURL(fileInput.files[0]);
}
Juan Mendes..
16
您可以通过将图像添加到DOM来确定图像的尺寸.知道比率后,您可以缩放图像以适合画布.
ratio = width / height;
width = height * ratio;
height = width / ratio;
无论图像是横向还是纵向,以下都应该有效.
var canvas = document.getElementById('image-canvas');
var canvas2 = document.getElementById('image-canvas2');
var ctx = canvas.getContext('2d');
document.getElementById('fileInput').addEventListener('change', imageLoader, false);
function imageLoader() {
var reader = new FileReader();
reader.Onload= function(event) {
var img = new Image();
img.Onload= function(){
var ct = document.getElementById('measure');
ct.appendChild(img);
var wrh = img.width / img.height;
var newWidth = canvas.width;
var newHeight = newWidth / wrh;
if (newHeight > canvas.height) {
newHeight = canvas.height;
newWidth = newHeight * wrh;
}
ct.removeChild(img);
ctx.drawImage(img,0,0, newWidth , newHeight);
}
img.src = reader.result;
}
reader.readAsDataURL(fileInput.files[0]);
}
/* Add image to the DOM here so user can't see it */
#measure { position: absolute; left: -10000px; top: -100000px;}
canvas { border: 1px solid red; }
你可以在这里玩
1> Juan Mendes..: 您可以通过将图像添加到DOM来确定图像的尺寸.知道比率后,您可以缩放图像以适合画布.
ratio = width / height;
width = height * ratio;
height = width / ratio;
无论图像是横向还是纵向,以下都应该有效.
var canvas = document.getElementById('image-canvas');
var canvas2 = document.getElementById('image-canvas2');
var ctx = canvas.getContext('2d');
document.getElementById('fileInput').addEventListener('change', imageLoader, false);
function imageLoader() {
var reader = new FileReader();
reader.Onload= function(event) {
var img = new Image();
img.Onload= function(){
var ct = document.getElementById('measure');
ct.appendChild(img);
var wrh = img.width / img.height;
var newWidth = canvas.width;
var newHeight = newWidth / wrh;
if (newHeight > canvas.height) {
newHeight = canvas.height;
newWidth = newHeight * wrh;
}
ct.removeChild(img);
ctx.drawImage(img,0,0, newWidth , newHeight);
}
img.src = reader.result;
}
reader.readAsDataURL(fileInput.files[0]);
}
/* Add image to the DOM here so user can't see it */
#measure { position: absolute; left: -10000px; top: -100000px;}
canvas { border: 1px solid red; }