使用JavaScript+canvas實(shí)現(xiàn)圖片裁剪
canvas是一個(gè)可以讓我們使用腳本繪圖的標(biāo)簽,它提供了一系列完整的屬性和方法。我們可以借此來實(shí)現(xiàn)圖形繪制,圖像處理甚至實(shí)現(xiàn)簡單的動畫和游戲制作。
canvas標(biāo)簽只有兩個(gè)屬性:width和height,用來設(shè)定畫布的寬和高,如果沒有通過標(biāo)簽屬性或者腳本來設(shè)置,默認(rèn)為300*150;
好了,canvas的介紹就先到這里,下面我們來看看javascript結(jié)合canvas實(shí)現(xiàn)圖片的裁剪代碼:
var selectObj = null;
function ImageCrop(canvasId, imageSource, x, y, width, height) {
var canvas = $("#" + canvasId);
if (canvas.length == 0 && imageSource) {
return;
}
function canvasMouseDown(e) {
StopSelect(e);
canvas.css("cursor", "default");
}
function canvasMouseMove(e) {
var canvasOffset = canvas.offset();
var pageX = e.pageX || event.targetTouches[0].pageX;
var pageY = e.pageY || event.targetTouches[0].pageY;
iMouseX = Math.floor(pageX - canvasOffset.left);
iMouseY = Math.floor(pageY - canvasOffset.top);
canvas.css("cursor", "default");
if (selectObj.bDragAll) {
canvas.css("cursor", "move");
canvas.data("drag", true);
var cx = iMouseX - selectObj.px;
cx = cx < 0 ? 0 : cx;
mx = ctx.canvas.width - selectObj.w;
cx = cx > mx ? mx : cx;
selectObj.x = cx;
var cy = iMouseY - selectObj.py;
cy = cy < 0 ? 0 : cy;
my = ctx.canvas.height - selectObj.h;
cy = cy > my ? my : cy;
selectObj.y = cy;
}
for (var i = 0; i < 4; i++) {
selectObj.bHow[i] = false;
selectObj.iCSize[i] = selectObj.csize;
}
// hovering over resize cubes
if (iMouseX > selectObj.x - selectObj.csizeh && iMouseX < selectObj.x + selectObj.csizeh &&
iMouseY > selectObj.y - selectObj.csizeh && iMouseY < selectObj.y + selectObj.csizeh) {
canvas.css("cursor", "pointer");
selectObj.bHow[0] = true;
selectObj.iCSize[0] = selectObj.csizeh;
}
if (iMouseX > selectObj.x + selectObj.w - selectObj.csizeh && iMouseX < selectObj.x + selectObj.w + selectObj.csizeh &&
iMouseY > selectObj.y - selectObj.csizeh && iMouseY < selectObj.y + selectObj.csizeh) {
canvas.css("cursor", "pointer");
selectObj.bHow[1] = true;
selectObj.iCSize[1] = selectObj.csizeh;
}
if (iMouseX > selectObj.x + selectObj.w - selectObj.csizeh && iMouseX < selectObj.x + selectObj.w + selectObj.csizeh &&
iMouseY > selectObj.y + selectObj.h - selectObj.csizeh && iMouseY < selectObj.y + selectObj.h + selectObj.csizeh) {
canvas.css("cursor", "pointer");
selectObj.bHow[2] = true;
selectObj.iCSize[2] = selectObj.csizeh;
}
if (iMouseX > selectObj.x - selectObj.csizeh && iMouseX < selectObj.x + selectObj.csizeh &&
iMouseY > selectObj.y + selectObj.h - selectObj.csizeh && iMouseY < selectObj.y + selectObj.h + selectObj.csizeh) {
canvas.css("cursor", "pointer");
selectObj.bHow[3] = true;
selectObj.iCSize[3] = selectObj.csizeh;
}
if (iMouseX > selectObj.x && iMouseX < selectObj.x + selectObj.w && iMouseY > selectObj.y && iMouseY < selectObj.y + selectObj.h) {
canvas.css("cursor", "move");
}
// in case of dragging of resize cubes
var iFW, iFH, iFX, iFY, mx, my;
if (selectObj.bDrag[0]) {
iFX = iMouseX - selectObj.px;
iFY = iMouseY - selectObj.py;
iFW = selectObj.w + selectObj.x - iFX;
iFH = selectObj.h + selectObj.y - iFY;
canvas.data("drag", true);
}
if (selectObj.bDrag[1]) {
iFX = selectObj.x;
iFY = iMouseY - selectObj.py;
iFW = iMouseX - selectObj.px - iFX;
iFH = selectObj.h + selectObj.y - iFY;
canvas.data("drag", true);
}
if (selectObj.bDrag[2]) {
iFX = selectObj.x;
iFY = selectObj.y;
iFW = iMouseX - selectObj.px - iFX;
iFH = iMouseY - selectObj.py - iFY;
canvas.data("drag", true);
}
if (selectObj.bDrag[3]) {
iFX = iMouseX - selectObj.px;
iFY = selectObj.y;
iFW = selectObj.w + selectObj.x - iFX;
iFH = iMouseY - selectObj.py - iFY;
canvas.data("drag", true);
}
if (iFW > selectObj.csizeh * 2 && iFH > selectObj.csizeh * 2) {
selectObj.w = iFW;
selectObj.h = iFH;
selectObj.x = iFX;
selectObj.y = iFY;
}
drawScene();
}
function canvasMouseOut() {
$(canvas).trigger("mouseup");
}
function canvasMouseUp() {
selectObj.bDragAll = false;
for (var i = 0; i < 4; i++) {
selectObj.bDrag[i] = false;
}
canvas.css("cursor", "default");
canvas.data("select", {
x: selectObj.x,
y: selectObj.y,
w: selectObj.w,
h: selectObj.h
});
selectObj.px = 0;
selectObj.py = 0;
}
function Selection(x, y, w, h) {
this.x = x; // initial positions
this.y = y;
this.w = w; // and size
this.h = h;
this.px = x; // extra variables to dragging calculations
this.py = y;
this.csize = 4; // resize cubes size
this.csizeh = 6; // resize cubes size (on hover)
this.bHow = [false, false, false, false]; // hover statuses
this.iCSize = [this.csize, this.csize, this.csize, this.csize]; // resize cubes sizes
this.bDrag = [false, false, false, false]; // drag statuses
this.bDragAll = false; // drag whole selection
}
Selection.prototype.draw = function () {
ctx.strokeStyle = '#666';
ctx.lineWidth = 2;
ctx.strokeRect(this.x, this.y, this.w, this.h);
// draw part of original image
if (this.w > 0 && this.h > 0) {
ctx.drawImage(image, this.x, this.y, this.w, this.h, this.x, this.y, this.w, this.h);
}
// draw resize cubes
ctx.fillStyle = '#999';
ctx.fillRect(this.x - this.iCSize[0], this.y - this.iCSize[0], this.iCSize[0] * 2, this.iCSize[0] * 2);
ctx.fillRect(this.x + this.w - this.iCSize[1], this.y - this.iCSize[1], this.iCSize[1] * 2, this.iCSize[1] * 2);
ctx.fillRect(this.x + this.w - this.iCSize[2], this.y + this.h - this.iCSize[2], this.iCSize[2] * 2, this.iCSize[2] * 2);
ctx.fillRect(this.x - this.iCSize[3], this.y + this.h - this.iCSize[3], this.iCSize[3] * 2, this.iCSize[3] * 2);
};
var drawScene = function () {
ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height); // clear canvas
// draw source image
ctx.drawImage(image, 0, 0, ctx.canvas.width, ctx.canvas.height);
// and make it darker
ctx.fillStyle = 'rgba(0, 0, 0, 0.5)';
ctx.fillRect(0, 0, ctx.canvas.width, ctx.canvas.height);
// draw selection
selectObj.draw();
canvas.mousedown(canvasMouseDown);
canvas.on("touchstart", canvasMouseDown);
};
var createSelection = function (x, y, width, height) {
var content = $("#imagePreview");
x = x || Math.ceil((content.width() - width) / 2);
y = y || Math.ceil((content.height() - height) / 2);
return new Selection(x, y, width, height);
};
var ctx = canvas[0].getContext("2d");
var iMouseX = 1;
var iMouseY = 1;
var image = new Image();
image.onload = function () {
selectObj = createSelection(x, y, width, height);
canvas.data("select", {
x: selectObj.x,
y: selectObj.y,
w: selectObj.w,
h: selectObj.h
});
drawScene();
};
image.src = imageSource;
canvas.mousemove(canvasMouseMove);
canvas.on("touchmove", canvasMouseMove);
var StopSelect = function (e) {
var canvasOffset = $(canvas).offset();
var pageX = e.pageX || event.targetTouches[0].pageX;
var pageY = e.pageY || event.targetTouches[0].pageY;
iMouseX = Math.floor(pageX - canvasOffset.left);
iMouseY = Math.floor(pageY - canvasOffset.top);
selectObj.px = iMouseX - selectObj.x;
selectObj.py = iMouseY - selectObj.y;
if (selectObj.bHow[0]) {
selectObj.px = iMouseX - selectObj.x;
selectObj.py = iMouseY - selectObj.y;
}
if (selectObj.bHow[1]) {
selectObj.px = iMouseX - selectObj.x - selectObj.w;
selectObj.py = iMouseY - selectObj.y;
}
if (selectObj.bHow[2]) {
selectObj.px = iMouseX - selectObj.x - selectObj.w;
selectObj.py = iMouseY - selectObj.y - selectObj.h;
}
if (selectObj.bHow[3]) {
selectObj.px = iMouseX - selectObj.x;
selectObj.py = iMouseY - selectObj.y - selectObj.h;
}
if (iMouseX > selectObj.x + selectObj.csizeh &&
iMouseX < selectObj.x + selectObj.w - selectObj.csizeh &&
iMouseY > selectObj.y + selectObj.csizeh &&
iMouseY < selectObj.y + selectObj.h - selectObj.csizeh) {
selectObj.bDragAll = true;
}
for (var i = 0; i < 4; i++) {
if (selectObj.bHow[i]) {
selectObj.bDrag[i] = true;
}
}
};
canvas.mouseout(canvasMouseOut);
canvas.mouseup(canvasMouseUp);
canvas.on("touchend", canvasMouseUp);
this.getImageData = function (previewID) {
var tmpCanvas = $("<canvas></canvas>")[0];
var tmpCtx = tmpCanvas.getContext("2d");
if (tmpCanvas && selectObj) {
tmpCanvas.width = selectObj.w;
tmpCanvas.height = selectObj.h;
tmpCtx.drawImage(image, selectObj.x, selectObj.y, selectObj.w, selectObj.h, 0, 0, selectObj.w, selectObj.h);
if (document.getElementById(previewID)) {
document.getElementById(previewID).src = tmpCanvas.toDataURL();
document.getElementById(previewID).style.border = "1px solid #ccc";
}
return tmpCanvas.toDataURL();
}
};
}
function autoResizeImage(maxWidth, maxHeight, objImg) {
var img = new Image();
img.src = objImg.src;
var hRatio;
var wRatio;
var ratio = 1;
var w = objImg.width;
var h = objImg.height;
wRatio = maxWidth / w;
hRatio = maxHeight / h;
if (w < maxWidth && h < maxHeight) {
return;
}
if (maxWidth == 0 && maxHeight == 0) {
ratio = 1;
} else if (maxWidth == 0) {
if (hRatio < 1) {
ratio = hRatio;
}
} else if (maxHeight == 0) {
if (wRatio < 1) {
ratio = wRatio;
}
} else if (wRatio < 1 || hRatio < 1) {
ratio = (wRatio <= hRatio ? wRatio : hRatio);
} else {
ratio = (wRatio <= hRatio ? wRatio : hRatio) - Math.floor(wRatio <= hRatio ? wRatio : hRatio);
}
if (ratio < 1) {
if (ratio < 0.5 && w < maxWidth && h < maxHeight) {
ratio = 1 - ratio;
}
w = w * ratio;
h = h * ratio;
}
objImg.height = h;
objImg.width = w;
}
小伙伴們拿去試試吧,希望大家能夠喜歡,有疑問就給我留言吧。
- 基于原生JS實(shí)現(xiàn)圖片裁剪
- js+jquery實(shí)現(xiàn)圖片裁剪功能
- php+js實(shí)現(xiàn)圖片的上傳、裁剪、預(yù)覽、提交示例
- 基于HTML5+JS實(shí)現(xiàn)本地圖片裁剪并上傳功能
- Cropper.js 實(shí)現(xiàn)裁剪圖片并上傳(PC端)
- 使用ImageMagick進(jìn)行圖片縮放、合成與裁剪(js+python)
- vue-cli結(jié)合Element-ui基于cropper.js封裝vue實(shí)現(xiàn)圖片裁剪組件功能
- Nodejs下使用gm圓形裁剪并合成圖片的示例
- cropper js基于vue的圖片裁剪上傳功能的實(shí)現(xiàn)代碼
- cropperjs實(shí)現(xiàn)裁剪圖片功能
相關(guān)文章
Tab頁界面 用jQuery及Ajax技術(shù)實(shí)現(xiàn)(php后臺)
到了B/S開發(fā)時(shí)代,網(wǎng)頁前端布局也把Tab頁的布局形式吸收了過來。特別是和Ajax技術(shù)結(jié)合起來,可以更充分發(fā)揮Tab頁的良好表現(xiàn)力和數(shù)據(jù)緩存的優(yōu)勢,是一種良好的網(wǎng)頁布局形式2011-10-10
jquery觸發(fā)a標(biāo)簽跳轉(zhuǎn)事件示例代碼
本文為大家詳細(xì)介紹下如何使用jquery觸發(fā)a標(biāo)簽的跳轉(zhuǎn)事件,感興趣的朋友可以參考下哈,希望對大家有所幫助2013-07-07
最佳6款用于移動網(wǎng)站開發(fā)的jQuery 圖片滑塊插件小結(jié)
隨著智能手機(jī)的普及,越來越多的用戶喜歡通過手機(jī)中瀏覽網(wǎng)頁。今天這篇文章為大家推薦最佳6款用于移動應(yīng)用的 jQuery 圖片滑塊插件,這些插件很好的處理了觸屏事件,效果平滑,幫助你構(gòu)建用戶體驗(yàn)良好的移動網(wǎng)站2012-07-07
JQuery實(shí)現(xiàn)table行折疊效果以JSON做數(shù)據(jù)源
這篇文章主要介紹JQuery實(shí)現(xiàn)的table行折疊效果并以JSON做數(shù)據(jù)源,需要的朋友可以參考下2014-05-05
騰訊與新浪的通過IP地址獲取當(dāng)前地理位置(省份)的接口
通過IP地址獲取當(dāng)前地理位置(省份)的接口,方便大家可以直接使用結(jié)合自己的系統(tǒng)。2010-07-07
jquery實(shí)現(xiàn)點(diǎn)擊向下展開菜單項(xiàng)(伸縮導(dǎo)航)效果
這篇文章主要介紹了jquery實(shí)現(xiàn)點(diǎn)擊向下展開菜單項(xiàng)(伸縮導(dǎo)航)效果,通過jquery遍歷及匹配頁面元素并動態(tài)修改頁面元素樣式實(shí)現(xiàn)該功能,需要的朋友可以參考下2015-08-08
jquery表單驗(yàn)證插件validation使用方法詳解
這篇文章主要為大家詳細(xì)介紹了jquery表單驗(yàn)證插件validation使用方法,具有一定的參考價(jià)值,感興趣的小伙伴們可以參考一下2017-01-01
google jQuery 引用文件,jQuery 引用地址集合(jquery 1.2.6至jquery1.5.2)
很多網(wǎng)站都是使用這種方式引入,客戶的瀏覽器可能已經(jīng)緩存過了 jquery??梢灾苯诱{(diào)用本地的,速度更快2011-04-04

