Javascript 如何在画布对象中保持图像的纵横比
关于纵横比的快速问题让我有点发疯。我的画布元素的固定尺寸为250x250(1:1)。然而,我正在画布上绘制的图像可能是任何大小/比例。显然,如果我试图强制图像为250x250,它看起来会失真 我试图使它尊重纵横比,但我得到了一个奇怪的画布对象重叠现在,我的悬停效果是有点关闭,因为它。我的数学是错误的,或者我将其应用于图像/画布的方式是错误的。如有任何帮助或建议,将不胜感激Javascript 如何在画布对象中保持图像的纵横比,javascript,html,canvas,Javascript,Html,Canvas,关于纵横比的快速问题让我有点发疯。我的画布元素的固定尺寸为250x250(1:1)。然而,我正在画布上绘制的图像可能是任何大小/比例。显然,如果我试图强制图像为250x250,它看起来会失真 我试图使它尊重纵横比,但我得到了一个奇怪的画布对象重叠现在,我的悬停效果是有点关闭,因为它。我的数学是错误的,或者我将其应用于图像/画布的方式是错误的。如有任何帮助或建议,将不胜感激 var NameSpace=NameSpace | |{}; NameSpace.Pixelator=(函数(){ 变量_
var NameSpace=NameSpace | |{};
NameSpace.Pixelator=(函数(){
变量_缓存={
“包装器”:null,
“画布”:null,
“ctx”:null,
“img”:新图像()
},
_配置={
“画布宽度”:250,
“画布高度”:250,
“iPlaying”:错误,
"明":3,,
“最大值”:100,
“扭曲值”:100,//默认情况下与扭曲最大值匹配
“初始值”:3,
“速度”:2.5,
“delta”:2.5,//delta(+/-step),默认情况下与速度匹配
“动画”:null,
“origImgWidth”:null,
“OrigighHeight”:null,
“imgHeightRatio”:null,
“imgWidthRatio”:null,
“newImgWidth”:null,
“newImgHeight”:null
},
_init=函数_init(){
_setupCache();
_setupCanvas();
_setupImage();
},
_setupCache=函数_setupCache(){
_cache.wrapper=$(“#虚拟包装器”);
_cache.canvas=document.getElementById('dummy-canvas');
_cache.ctx=_cache.canvas.getContext('2d');
},
_setupCanvas=函数_setupCanvas(){
_cache.ctx.mozimagesoothingEnabled=false;
_cache.ctx.webkitmagesmoothingEnabled=false;
_cache.ctx.imageSmoothingEnabled=false;
},
_setupImage=函数_setupImage(){
$(_cache.img).on('load',function()){
_调整图像比例();
_像素();
_赋值事件();
});
_cache.img.src=_cache.canvas.getAttribute('data-src');
},
_adjustImageScale=功能_adjustImageScale(){
var标度高度,
标度宽度;
_config.origImgWidth=\u cache.img.width;
_config.origImgHeight=\u cache.img.height;
_config.imghlightratio=\u config.origImgHeight/\u config.origImgWidth;
_config.imgWidthRatio=\u config.origImgWidth/\u config.origImgHeight;
scaledHeight=数学圆(250*_config.imghtRatio);
scaledWidth=Math.round(250*_config.imgWidthRatio);
如果(标度高度<250){
_config.newImgHeight=250;
_config.newImgWidth=Math.round(_config.newImgHeight*_config.imgWidthRatio);
}否则如果(缩放宽度<250){
_config.newImgWidth=250;
_config.newImgHeight=Math.round(_config.newImgWidth*_config.imgheight比率);
}
},
_assignEvents=函数_assignEvents(){
_cache.wrapper.on('mouseenter',_mouseEnterHandler);
_cache.wrapper.on('mouseleave',_mouseLeaveHandler);
},
_mouseEnterHandler=函数_mouseEnterHandler(e){
_config.delta=--u config.speed;
如果(_config.isPlaying==false){
_config.isplay=true;
_制作动画();
}
},
_mouseLeaveHandler=函数_mouseLeaveHandler(e){
_config.delta=_config.speed;
如果(_config.isPlaying==false){
_config.isplay=true;
_制作动画();
}
},
_像素=函数_像素(val){
变量大小=val?val*0.01:1,
w=Math.ceil(_config.newImgWidth*size),
h=Math.ceil(_config.newImgHeight*size);
_cache.ctx.drawImage(_cache.img,0,0,w,h);
_cache.ctx.drawImage(_cache.canvas,0,0,w,h,0,0,_config.canvaswitch,_config.canvaswitch);
},
_动画=函数_animate(){
//通过鼠标移过/移出增量设置增加/减少
_config.value+=\u config.delta;
如果(_config.trunteValue>=_config.truntemax | | | | | u config.trunteValue您的代码将w*h
区域(非方形)采样到\u config.canvasWidth*\u config.canvashight
区域(方形)。以下更改似乎为我修复了您的示例:
//旧代码
_cache.ctx.drawImage(_cache.canvas,0,0,w,h,0,0,_config.canvaswitch,_config.canvaswitch);
//新代码
_cache.ctx.drawImage(_cache.canvas,0,0,w,h,0,0,_config.newImgWidth,_config.newImgHeight);
DOH!这正是我需要另一双眼睛的原因。非常感谢!
var NameSpace = NameSpace || {};
NameSpace.Pixelator = (function() {
var _cache = {
'wrapper' : null,
'canvas' : null,
'ctx' : null,
'img' : new Image()
},
_config = {
'canvasWidth' : 250,
'canvasHeight' : 250,
'isPlaying' : false,
'distortMin' : 3,
'distortMax' : 100,
'distortValue' : 100, // matches distortMax by default
'initDistortValue' : 3,
'speed' : 2.5,
'delta' : 2.5, // delta (+/- step), matches speed by default
'animation' : null,
'origImgWidth' : null,
'origImgHeight' : null,
'imgHeightRatio' : null,
'imgWidthRatio' : null,
'newImgWidth' : null,
'newImgHeight' : null
},
_init = function _init() {
_setupCache();
_setupCanvas();
_setupImage();
},
_setupCache = function _setupCache() {
_cache.wrapper = $('#dummy-wrapper');
_cache.canvas = document.getElementById('dummy-canvas');
_cache.ctx = _cache.canvas.getContext('2d');
},
_setupCanvas = function _setupCanvas() {
_cache.ctx.mozImageSmoothingEnabled = false;
_cache.ctx.webkitImageSmoothingEnabled = false;
_cache.ctx.imageSmoothingEnabled = false;
},
_setupImage = function _setupImage() {
$(_cache.img).on('load', function() {
_adjustImageScale();
_pixelate();
_assignEvents();
});
_cache.img.src = _cache.canvas.getAttribute('data-src');
},
_adjustImageScale = function _adjustImageScale() {
var scaledHeight,
scaledWidth;
_config.origImgWidth = _cache.img.width;
_config.origImgHeight = _cache.img.height;
_config.imgHeightRatio = _config.origImgHeight / _config.origImgWidth;
_config.imgWidthRatio = _config.origImgWidth / _config.origImgHeight;
scaledHeight = Math.round(250 * _config.imgHeightRatio);
scaledWidth = Math.round(250 * _config.imgWidthRatio);
if (scaledHeight < 250) {
_config.newImgHeight = 250;
_config.newImgWidth = Math.round(_config.newImgHeight * _config.imgWidthRatio);
} else if (scaledWidth < 250) {
_config.newImgWidth = 250;
_config.newImgHeight = Math.round(_config.newImgWidth * _config.imgHeightRatio);
}
},
_assignEvents = function _assignEvents() {
_cache.wrapper.on('mouseenter', _mouseEnterHandler);
_cache.wrapper.on('mouseleave', _mouseLeaveHandler);
},
_mouseEnterHandler = function _mouseEnterHandler(e) {
_config.delta = -_config.speed;
if (_config.isPlaying === false) {
_config.isPlaying = true;
_animate();
}
},
_mouseLeaveHandler = function _mouseLeaveHandler(e) {
_config.delta = _config.speed;
if (_config.isPlaying === false) {
_config.isPlaying = true;
_animate();
}
},
_pixelate = function _pixelate(val) {
var size = val ? val * 0.01 : 1,
w = Math.ceil(_config.newImgWidth * size),
h = Math.ceil(_config.newImgHeight * size);
_cache.ctx.drawImage(_cache.img, 0, 0, w, h);
_cache.ctx.drawImage(_cache.canvas, 0, 0, w, h, 0, 0, _config.canvasWidth, _config.canvasHeight);
},
_animate = function _animate() {
// increase/decrese with delta set by mouse over/out
_config.distortValue += _config.delta;
if (_config.distortValue >= _config.distortMax || _config.distortValue <= _config.distortMin) {
_config.isPlaying = false;
cancelAnimationFrame(_config.animation);
return;
} else {
// pixelate
_pixelate(_config.distortValue);
_config.animation = requestAnimationFrame(_animate);
}
};
return {
init: _init
};
})();
NameSpace.Pixelator.init();