Canvas实例教程：图像大小调整和裁剪

学习如何使用JavaScript和HTML5 Canvas元素来调整和裁剪图像(Resizing and Cropping Images with Canvas。)，适用于图片编辑器、照片分享等应用场景。 Tutorial links： http://tympanus.net/codrops/2014/10/30/resizing-cropping-images-canvas/； Read more: http://stackoverflow.com/questions/18922880/html5-canvas-resize-downscale-image-high-quality

canvas，教程，图像处理

《three.js使用多个渐变torus模拟光环光晕》申请公开！

第三方库
作品简介 29016
使用帮助
常用链接

HTML
CSS
JavaScript
Result

编译

JavaScript

if (window.location.protocol == 'file:') {
    alert('To test this demo properly please use a local server such as XAMPP or WAMP. See README.md for more details.');
}

var resizeableImage = function(image_target) {
    // Some variable and settings
    var $container,
        orig_src = new Image(),
        image_target = $(image_target).get(0),
        event_state = {},
        constrain = false,
        min_width = 60, // Change as required
        min_height = 60,
        max_width = 800, // Change as required
        max_height = 900,
        resize_canvas = document.createElement('canvas');

init = function() {

// When resizing, we will always use this copy of the original as the base
        orig_src.src = image_target.src;

// Wrap the image with the container and add resize handles
        $(image_target).wrap('<div class="resize-container"></div>')
            .before('<span class="resize-handle resize-handle-nw"></span>')
            .before('<span class="resize-handle resize-handle-ne"></span>')
            .after('<span class="resize-handle resize-handle-se"></span>')
            .after('<span class="resize-handle resize-handle-sw"></span>');

// Assign the container to a variable
        $container = $(image_target).parent('.resize-container');

// Add events
        $container.on('mousedown touchstart', '.resize-handle', startResize);
        $container.on('mousedown touchstart', 'img', startMoving);
        $('.js-crop').on('click', crop);
    };

startResize = function(e) {
        e.preventDefault();
        e.stopPropagation();
        saveEventState(e);
        $(document).on('mousemove touchmove', resizing);
        $(document).on('mouseup touchend', endResize);
    };

endResize = function(e) {
        e.preventDefault();
        $(document).off('mouseup touchend', endResize);
        $(document).off('mousemove touchmove', resizing);
    };

saveEventState = function(e) {
        // Save the initial event details and container state
        event_state.container_width = $container.width();
        event_state.container_height = $container.height();
        event_state.container_left = $container.offset().left;
        event_state.container_top = $container.offset().top;
        event_state.mouse_x = (e.clientX || e.pageX || e.originalEvent.touches[0].clientX) + $(window).scrollLeft();
        event_state.mouse_y = (e.clientY || e.pageY || e.originalEvent.touches[0].clientY) + $(window).scrollTop();

// This is a fix for mobile safari
        // For some reason it does not allow a direct copy of the touches property
        if (typeof e.originalEvent.touches !== 'undefined') {
            event_state.touches = [];
            $.each(e.originalEvent.touches, function(i, ob) {
                event_state.touches[i] = {};
                event_state.touches[i].clientX = 0 + ob.clientX;
                event_state.touches[i].clientY = 0 + ob.clientY;
            });
        }
        event_state.evnt = e;
    };

resizing = function(e) {
        var mouse = {},
            width, height, left, top, offset = $container.offset();
        mouse.x = (e.clientX || e.pageX || e.originalEvent.touches[0].clientX) + $(window).scrollLeft();
        mouse.y = (e.clientY || e.pageY || e.originalEvent.touches[0].clientY) + $(window).scrollTop();

// Position image differently depending on the corner dragged and constraints
        if ($(event_state.evnt.target).hasClass('resize-handle-se')) {
            width = mouse.x - event_state.container_left;
            height = mouse.y - event_state.container_top;
            left = event_state.container_left;
            top = event_state.container_top;
        } else if ($(event_state.evnt.target).hasClass('resize-handle-sw')) {
            width = event_state.container_width - (mouse.x - event_state.container_left);
            height = mouse.y - event_state.container_top;
            left = mouse.x;
            top = event_state.container_top;
        } else if ($(event_state.evnt.target).hasClass('resize-handle-nw')) {
            width = event_state.container_width - (mouse.x - event_state.container_left);
            height = event_state.container_height - (mouse.y - event_state.container_top);
            left = mouse.x;
            top = mouse.y;
            if (constrain || e.shiftKey) {
                top = mouse.y - ((width / orig_src.width * orig_src.height) - height);
            }
        } else if ($(event_state.evnt.target).hasClass('resize-handle-ne')) {
            width = mouse.x - event_state.container_left;
            height = event_state.container_height - (mouse.y - event_state.container_top);
            left = event_state.container_left;
            top = mouse.y;
            if (constrain || e.shiftKey) {
                top = mouse.y - ((width / orig_src.width * orig_src.height) - height);
            }
        }

// Optionally maintain aspect ratio
        if (constrain || e.shiftKey) {
            height = width / orig_src.width * orig_src.height;
        }

if (width > min_width && height > min_height && width < max_width && height < max_height) {
            // To improve performance you might limit how often resizeImage() is called
            resizeImage(width, height);
            // Without this Firefox will not re-calculate the the image dimensions until drag end
            $container.offset({
                'left': left,
                'top': top
            });
        }
    }

resizeImage = function(width, height) {
        resize_canvas.width = width;
        resize_canvas.height = height;
        resize_canvas.getContext('2d').drawImage(orig_src, 0, 0, width, height);
        $(image_target).attr('src', resize_canvas.toDataURL("image/png"));
    };

startMoving = function(e) {
        e.preventDefault();
        e.stopPropagation();
        saveEventState(e);
        $(document).on('mousemove touchmove', moving);
        $(document).on('mouseup touchend', endMoving);
    };

endMoving = function(e) {
        e.preventDefault();
        $(document).off('mouseup touchend', endMoving);
        $(document).off('mousemove touchmove', moving);
    };

moving = function(e) {
        var mouse = {},
            touches;
        e.preventDefault();
        e.stopPropagation();

touches = e.originalEvent.touches;

mouse.x = (e.clientX || e.pageX || touches[0].clientX) + $(window).scrollLeft();
        mouse.y = (e.clientY || e.pageY || touches[0].clientY) + $(window).scrollTop();
        $container.offset({
            'left': mouse.x - (event_state.mouse_x - event_state.container_left),
            'top': mouse.y - (event_state.mouse_y - event_state.container_top)
        });
        // Watch for pinch zoom gesture while moving
        if (event_state.touches && event_state.touches.length > 1 && touches.length > 1) {
            var width = event_state.container_width,
                height = event_state.container_height;
            var a = event_state.touches[0].clientX - event_state.touches[1].clientX;
            a = a * a;
            var b = event_state.touches[0].clientY - event_state.touches[1].clientY;
            b = b * b;
            var dist1 = Math.sqrt(a + b);

a = e.originalEvent.touches[0].clientX - touches[1].clientX;
            a = a * a;
            b = e.originalEvent.touches[0].clientY - touches[1].clientY;
            b = b * b;
            var dist2 = Math.sqrt(a + b);

var ratio = dist2 / dist1;

width = width * ratio;
            height = height * ratio;
            // To improve performance you might limit how often resizeImage() is called
            resizeImage(width, height);
        }
    };

crop = function() {
        //Find the part of the image that is inside the crop box
        var crop_canvas,
            left = $('.overlay').offset().left - $container.offset().left,
            top = $('.overlay').offset().top - $container.offset().top,
            width = $('.overlay').width(),
            height = $('.overlay').height();

crop_canvas = document.createElement('canvas');
        crop_canvas.width = width;
        crop_canvas.height = height;

crop_canvas.getContext('2d').drawImage(image_target, left, top, width, height, 0, 0, width, height);
      
        //window.open(crop_canvas.toDataURL("image/png")); 
        //Noted by iefreer 2019.03, above line of code doesn't work now as Chrome has removed top frame navigation, replaced with codes below instead.
        var iframe = "<iframe width='100%' height='100%' src='" + crop_canvas.toDataURL("image/png") + "'></iframe>"
        var x = window.open();
        x.document.open();
        x.document.write(iframe);
        x.document.close();      
    }

init();
};

// Kick everything off with the target image
resizeableImage($('.resize-image'));

编译

CSS

@import url(https://fonts.googleapis.com/css?family=Raleway:400,500,700);
article,
aside,
details,
figcaption,
figure,
footer,
header,
hgroup,
main,
nav,
section,
summary {
    display: block;
}
audio,
canvas,
video {
    display: inline-block;
}
audio:not([controls]) {
    display: none;
    height: 0;
}
[hidden] {
    display: none;
}
html {
    font-family: sans-serif;
    -ms-text-size-adjust: 100%;
    -webkit-text-size-adjust: 100%;
}
body {
    margin: 0;
}
a:focus {
    outline: thin dotted;
}
a:active,
a:hover {
    outline: 0;
}
h1 {
    font-size: 2em;
    margin: 0.67em 0;
}
abbr[title] {
    border-bottom: 1px dotted;
}
b,
strong {
    font-weight: bold;
}
dfn {
    font-style: italic;
}
hr {
    -moz-box-sizing: content-box;
    box-sizing: content-box;
    height: 0;
}
mark {
    background: #ff0;
    color: #000;
}
code,
kbd,
pre,
samp {
    font-family: monospace, serif;
    font-size: 1em;
}
pre {
    white-space: pre-wrap;
}
q {
    quotes: "\201C" "\201D" "\2018" "\2019";
}
small {
    font-size: 80%;
}
sub,
sup {
    font-size: 75%;
    line-height: 0;
    position: relative;
    vertical-align: baseline;
}
sup {
    top: -0.5em;
}
sub {
    bottom: -0.25em;
}
img {
    border: 0;
}
svg:not(:root) {
    overflow: hidden;
}
figure {
    margin: 0;
}
fieldset {
    border: 1px solid #c0c0c0;
    margin: 0 2px;
    padding: 0.35em 0.625em 0.75em;
}
legend {
    border: 0;
    padding: 0;
}
button,
input,
select,
textarea {
    font-family: inherit;
    font-size: 100%;
    margin: 0;
}
button,
input {
    line-height: normal;
}
button,
select {
    text-transform: none;
}
button,
html input[type="button"],
input[type="reset"],
input[type="submit"] {
    -webkit-appearance: button;
    cursor: pointer;
}
button[disabled],
html input[disabled] {
    cursor: default;
}
input[type="checkbox"],
input[type="radio"] {
    box-sizing: border-box;
    padding: 0;
}
input[type="search"] {
    -webkit-appearance: textfield;
    -moz-box-sizing: content-box;
    -webkit-box-sizing: content-box;
    box-sizing: content-box;
}
input[type="search"]::-webkit-search-cancel-button,
input[type="search"]::-webkit-search-decoration {
    -webkit-appearance: none;
}
button::-moz-focus-inner,
input::-moz-focus-inner {
    border: 0;
    padding: 0;
}
textarea {
    overflow: auto;
    vertical-align: top;
}
table {
    border-collapse: collapse;
    border-spacing: 0;
}
@font-face {
    font-weight: normal;
    font-style: normal;
    font-family: 'codropsicons';
    src: url('../fonts/codropsicons/codropsicons.eot');
    src: url('../fonts/codropsicons/codropsicons.eot?#iefix') format('embedded-opentype'), url('../fonts/codropsicons/codropsicons.woff') format('woff'), url('../fonts/codropsicons/codropsicons.ttf') format('truetype'), url('../fonts/codropsicons/codropsicons.svg#codropsicons') format('svg');
}
*,
*:after,
*:before {
    -webkit-box-sizing: border-box;
    box-sizing: border-box;
}
.clearfix:before,
.clearfix:after {
    content: '';
    display: table;
}
.clearfix:after {
    clear: both;
}
body {
    background: #88abc2;
    color: #ebf7f8;
    font-weight: 500;
    font-size: 1em;
    font-family: 'Raleway', Arial, sans-serif;
}
a {
    color: #d0e0eb;
    text-decoration: none;
    outline: none;
}
a:hover,
a:focus {
    color: #fff;
}
.content {
    max-width: 1290px;
    padding: 0 1em;
    margin: 0 auto;
    text-align: center;
}
.component {
    position: relative;
    background: url(/uploads/1903/gridme.png) repeat center center;
    padding: 4em;
    height: 500px;
    border: 3px solid #49708a;
    max-width: 901px;
    /* Header */
    
    overflow: hidden;
    margin: 0 auto;
}
.codrops-header {
    padding: 0 0 2em;
    letter-spacing: -1px;
}
.codrops-header h1 {
    font-weight: 800;
    font-size: 2.5em;
    line-height: 1.3;
    margin: 0.25em auto;
}
.codrops-header h1 span,
.a-tip {
    color: #49708a;
}
.a-tip {
    padding: 1em;
}
.a-tip span {
    border: 2px solid #fff;
    color: #fff;
    /* Top Navigation Style */
    
    display: inline-block;
    padding: 0 5px;
}
.codrops-top {
    width: 100%;
    text-transform: uppercase;
    font-weight: 700;
    font-size: 0.69em;
    line-height: 2.2;
}
.codrops-top a {
    display: inline-block;
    padding: 1em 2em;
    text-decoration: none;
    letter-spacing: 1px;
}
.codrops-top span.right {
    float: right;
}
.codrops-top span.right a {
    display: block;
    float: left;
}
.codrops-icon:before {
    margin: 0 4px;
    text-transform: none;
    font-weight: normal;
    font-style: normal;
    font-variant: normal;
    font-family: 'codropsicons';
    line-height: 1;
    speak: none;
    -webkit-font-smoothing: antialiased;
}
.codrops-icon-drop:before {
    content: "\e001";
}
.codrops-icon-prev:before {
    content: "\e004";
}
.codrops-demos a {
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 1px;
    padding: 0.5em 1em;
    margin: 5px;
    display: inline-block;
    border: 1px solid black;
    border-color: initial;
    border-radius: 4px;
}
.codrops-demos a.current-demo {
    color: #74777b;
}
.related {
    text-align: center;
    padding: 4em 0 2em;
}
.related > a {
    width: calc(100% - 20px);
    max-width: 340px;
    border: 2px solid #49708a;
    display: inline-block;
    text-align: center;
    vertical-align: top;
    margin: 20px 10px;
    padding: 25px;
}
.related a img {
    max-width: 100%;
    opacity: 0.8;
}
.related a:hover img,
.related a:active img {
    opacity: 1;
}
.related a h3 {
    margin: 0;
    padding: 0.5em 0 0.3em;
    max-width: 300px;
    /* Demo ad design */
    
    text-align: left;
    min-height: 60px;
}
body #cdawrap {
    background: rgba(0, 0, 0, 0.05);
    top: 50px;
    border: none;
}
body #cdawrap a {
    color: #fff !important;
}
body #cda-remove {
    color: #fff;
}
@media screen and (max-width: 27em) {
    .codrops-icon {
        font-size: 1.5em;
    }
    .codrops-icon span {
        display: none;
    }
}
.resize-container {
    position: relative;
    display: inline-block;
    cursor: move;
    margin: 0 auto;
}
.resize-container img {
    display: block;
}
.resize-container:hover img,
.resize-container:active img {
    outline: 2px dashed rgba(222, 60, 80, .9);
}
.resize-handle-ne,
.resize-handle-se,
.resize-handle-nw,
.resize-handle-sw {
    position: absolute;
    display: block;
    width: 10px;
    height: 10px;
    background: rgba(222, 60, 80, .9);
    z-index: 999;
}
.resize-handle-nw {
    top: -5px;
    left: -5px;
    cursor: nw-resize;
}
.resize-handle-sw {
    bottom: -5px;
    left: -5px;
    cursor: sw-resize;
}
.resize-handle-ne {
    top: -5px;
    right: -5px;
    cursor: ne-resize;
}
.resize-handle-se {
    bottom: -5px;
    right: -5px;
    cursor: se-resize;
}
.overlay {
    position: absolute;
    left: 50%;
    top: 50%;
    margin-left: -100px;
    margin-top: -100px;
    z-index: 999;
    width: 200px;
    height: 200px;
    border: solid 2px rgba(222, 60, 80, .9);
    box-sizing: content-box;
    pointer-events: none;
}
.overlay:after,
.overlay:before {
    content: '';
    position: absolute;
    display: block;
    width: 204px;
    height: 40px;
    border-left: dashed 2px rgba(222, 60, 80, .9);
    border-right: dashed 2px rgba(222, 60, 80, .9);
}
.overlay:before {
    top: 0;
    margin-left: -2px;
    margin-top: -40px;
}
.overlay:after {
    bottom: 0;
    margin-left: -2px;
    margin-bottom: -40px;
}
.overlay-inner:after,
.overlay-inner:before {
    content: '';
    position: absolute;
    display: block;
    width: 40px;
    height: 204px;
    border-top: dashed 2px rgba(222, 60, 80, .9);
    border-bottom: dashed 2px rgba(222, 60, 80, .9);
}
.overlay-inner:before {
    left: 0;
    margin-left: -40px;
    margin-top: -2px;
}
.overlay-inner:after {
    right: 0;
    margin-right: -40px;
    margin-top: -2px;
}
.btn-crop {
    position: absolute;
    vertical-align: bottom;
    right: 5px;
    bottom: 5px;
    padding: 6px 10px;
    z-index: 999;
    background-color: #de3c50;
    border: none;
    border-radius: 5px;
    color: #fff;
}
.btn-crop img {
    vertical-align: middle;
    margin-left: 8px;
}

HTML

canvas，教程，图像处理

编辑器支持Emmet

快捷键

canvas，教程，图像处理

编辑器支持Emmet

快捷键

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