前端图片裁剪已经是很常见的需求了,在 react 的项目中推荐使用 react-image-crop 库,能勾勒出裁剪区域、宽高比例限制等等,但是还是有很多东西需要我们来做的,比如以下问题:
react-image-crop 的基本使用
import ReactCrop from "react-image-crop";
import "react-image-crop/dist/ReactCrop.css";
const cropOnChange = (newCrop: any) => {
};
const onImageLoaded = (image: any) => {
};
<ReactCrop
src={
src}
crop={
crop}
onChange={
cropOnChange}
onImageLoaded={
onImageLoaded}
>
{
props.children}
</ReactCrop>;
如果连展示位的最小宽高都不满足,那还裁剪什么
export function getImgSize(src: any, w: number, h: number): Promise<any> {
return new Promise((resolve, reject) => {
if (!src) return;
const img = document.createElement("img");
img.src = src;
img.onload = function() {
const {
width, height } = img;
if (width < w || height < h) {
reject(`请上传宽大于${
w},高大于${
h}的图片`);
return;
}
resolve({
width, height, img });
};
});
}
有的图片尺寸很大,但是我们要显示在一个屏幕之中,那么要采取原图按比例缩放,所以定高和定宽成了一个选择,那么会出现另一个问题,后面再说。
假设我们决定了定高:
const initImage = (image: any) => {
const {
width, height } = image;
// 计算出现在高度和定高的比例
let radio = height / config.imgMinWH.h;
// 那么现在宽度值
let cW = width / radio,
cH = config.imgMinWH.h;
if (width === 900) {
cW = 900;
radio = 1;
let wRadio = cW / width;
cH = height * wRadio;
}
// 设置image的宽高
image.width = cW;
image.height = cH;
setScaleRadio(radio);
setCrop({
...crop, ...{
x: 0, y: 0, width: cW, unit: "px" } });
};
裁剪的话使用 canvas 来裁剪,那么有个很重要的问题,就是图片的跨域问题,图片不在一个域下的话,使用 canvas 会污染画布,这个时候别急,将使用其他方法来解决这个问题,oss 的话开启图片的 get 操作即可
const canvas = document.createElement("canvas");
const ctx: any = canvas.getContext("2d");
const canvasImage = () => {
const img = new Image();
img.crossOrigin = "Anonymous";
img.src = signatureUrl(props.src || "", false);
common.showLoading();
img.onload = function() {
const {
x, y, width, height } = crop;
canvas.width = Math.floor(width * scaleRadio);
canvas.height = Math.floor(height * scaleRadio);
ctx.drawImage(
img,
Math.floor(x * scaleRadio),
Math.floor(y * scaleRadio),
img.width,
img.height,
0,
0,
img.width,
img.height
);
getImageFileInfo().then(fileInfo => {
// 上传图片到接口
uploadImage(fileInfo);
});
};
};
const getImageFileInfo = (): Promise<any> => {
return new Promise((resolve, reject) => {
// 将canvas转成图片base64的url,可以直接打开
// console.log(canvas.toDataURL('image/png'));
// 将canvas转成Blob格式的二进制数据
canvas.toBlob(blob => {
if (!blob) {
console.error("Canvas is empty");
return;
}
resolve(blob);
});
});
};
const canvas = document.createElement("canvas");
const ctx: any = canvas.getContext("2d");
const requestImg = () => {
ctx.clearRect(0, 0, canvas.width, canvas.height);
const xhr = new XMLHttpRequest();
xhr.onload = function() {
const url = URL.createObjectURL(this.response);
const img = new Image();
img.onload = function() {
canvas.width = img.naturalWidth;
canvas.height = img.naturalHeight;
ctx.drawImage(this, 0, 0, img.naturalWidth, img.naturalHeight);
URL.revokeObjectURL(url);
const base64 = canvas.toDataURL();
console.log(base64);
};
img.src = url;
};
xhr.open("GET", props.src || "", true);
xhr.responseType = "blob";
xhr.send();
};
import React, {
useState, useEffect } from "react";
import ReactCrop from "react-image-crop";
import {
SuperUpload } from "@/components/Base";
import defaultConfig from "./config";
import "react-image-crop/dist/ReactCrop.css";
import {
multipartUpload } from "@/components/Upload/method";
import {
signatureUrl } from "@/utils/oss";
const style = require("./index.less");
export interface CoreImageInterface {
imgMinWH?: {
w: number, h: number };
visible: boolean;
value?: string;
config?: any;
src?: string;
aspect?: number;
openCore: Function;
srcChange: Function;
onCancel?: Function;
onChange?: Function;
}
export function getImgSize(src: any, w: number, h: number): Promise<any> {
return new Promise((resolve, reject) => {
if (!src) return;
const img = document.createElement("img");
img.src = src;
img.onload = function() {
const {
width, height } = img;
if (width < w || height < h) {
reject(`请上传宽大于${
w},高大于${
h}的图片`);
return;
}
resolve({
width, height, img });
};
});
}
export function makeUploadName() {
return "core-image/" + +new Date();
}
const canvas = document.createElement("canvas");
const ctx: any = canvas.getContext("2d");
const CoreImage: React.FC<CoreImageInterface> = props => {
const [crop, setCrop]: [any, Function] = useState({
aspect: props.aspect || 3 / 1
});
const [scaleRadio, setScaleRadio] = useState(1);
const [visible, setVisible] = useState(false);
const [src, setSrc] = useState("");
const config = {
...defaultConfig, ...props.config };
useEffect(() => {
setVisible(props.visible);
if (!props.visible) {
setCrop({
aspect: props.aspect || 3 / 1 });
setSrc("");
return;
}
initCrop();
}, [props.visible]);
const initCrop = () => {
const img = new Image();
const src = signatureUrl(props.src || "", false);
img.src = src;
img.onload = function() {
setSrc(src || "");
};
};
const initImage = (image: any) => {
const {
width, height } = image;
let radio = height / config.imgMinWH.h;
let cW = width / radio,
cH = config.imgMinWH.h;
if (width === 900) {
cW = 900;
radio = 1;
let wRadio = cW / width;
cH = height * wRadio;
}
image.width = cW;
image.height = cH;
setScaleRadio(radio);
setCrop({
...crop, ...{
x: 0, y: 0, width: cW, unit: "px" } });
};
const onImageLoaded = (image: any) => {
initImage(image);
};
const cropOnChange = (newCrop: any) => {
if (newCrop.width * scaleRadio < config.imgMinWH.w) return;
setCrop(newCrop);
// console.log(crop);
};
const canvasImage = () => {
const img = new Image();
img.crossOrigin = "Anonymous";
img.src = signatureUrl(props.src || "", false);
common.showLoading();
img.onload = function() {
const {
x, y, width, height } = crop;
canvas.width = Math.floor(width * scaleRadio);
canvas.height = Math.floor(height * scaleRadio);
ctx.drawImage(
img,
Math.floor(x * scaleRadio),
Math.floor(y * scaleRadio),
img.width,
img.height,
0,
0,
img.width,
img.height
);
getImageFileInfo().then(fileInfo => {
uploadImage(fileInfo);
});
};
};
const uploadImage = (fileInfo: Blob) => {
const fileName = makeUploadName();
multipartUpload({
fileName, fileInfo }).then((res: any) => {
common.hideLoading();
props.onChange && props.onChange(res.name);
});
};
// ajax请求图片来解决跨域
// const requestImg = () => {
// ctx.clearRect(0, 0, canvas.width, canvas.height);
// const xhr = new XMLHttpRequest();
// xhr.onload = function() {
// const url = URL.createObjectURL(this.response);
// const img = new Image();
// img.onload = function() {
// canvas.width = img.naturalWidth;
// canvas.height = img.naturalHeight;
// ctx.drawImage(this, 0, 0, img.naturalWidth, img.naturalHeight);
// URL.revokeObjectURL(url);
// const base64 = canvas.toDataURL();
// console.log(base64);
// };
// img.src = url;
// };
// xhr.open('GET', props.src || '', true);
// xhr.responseType = 'blob';
// xhr.send();
// };
const getImageFileInfo = (): Promise<any> => {
return new Promise((resolve, reject) => {
// console.log(canvas.toDataURL('image/png'));
canvas.toBlob(blob => {
if (!blob) {
console.error("Canvas is empty");
return;
}
resolve(blob);
});
});
};
const openCore = () => {
if (props.src) props.openCore();
};
const onCancel = () => {
props.onCancel && props.onCancel();
};
const onConfirm = () => {
canvasImage();
};
return (
<div>
<>
<div className={
style.showBox}>
<img
style={
{
width: `${
config.thumbImageWH.w}px`,
height: `${
config.thumbImageWH.h}px`
}}
src={
signatureUrl(props.value || "")}
alt=""
/>
<div className={
style.againOp}>
<SuperUpload
accept=".png,.jpg"
isSelect={
true}
showUploadList={
false}
listType="text"
imgMinWH={
config.imgMinWH}
imgText={
<div className={
style.btn}>重新上传</div>}
onChange={
res => props.srcChange(res)}
></SuperUpload>
<div onClick={
openCore} className={
style.btn}>
裁剪头图
</div>
</div>
</div>
</>
<>
{
visible && src ? (
<div className={
style.container}>
<div className={
style.core}>
<ReactCrop
src={
src}
crop={
crop}
onChange={
cropOnChange}
onImageLoaded={
onImageLoaded}
>
{
props.children}
</ReactCrop>
<div
style={
{
top: `${
crop.y + crop.height / 2 - 15.5}px`,
left: `${
crop.x + crop.width / 2 - 46}px`
}}
className={
style.size}
>{
`${
Math.floor(crop.width * scaleRadio)} × ${
Math.floor(
crop.height * scaleRadio
)}`}</div>
<div
style={
{
top: `${
crop.height + crop.y + 10}px`,
left: `${
crop.width + crop.x - 146}px`
}}
className={
style.op}
>
<div onClick={
onCancel} className={
style.btn}>
取消
</div>
<div onClick={
onConfirm} className={
style.btn}>
确定
</div>
</div>
</div>
</div>
) : null}
</>
</div>
);
};
export default CoreImage;