How to deal with image cropping and rotation problems encountered in Vue development

How to deal with image cropping and rotation problems encountered in Vue development

During the Vue development process, we often encounter the need to crop and rotate images. For example, when a user uploads an avatar, he or she needs to crop it into a round or square avatar, or the image needs to be rotated at a certain angle. This article will introduce a common processing method to solve these problems.

1. Picture cropping

Picture cropping refers to cropping the original picture into a certain shape according to the needs, such as circle, square, ellipse, etc. In Vue, you can use some open source image editing libraries to implement image cropping functions, such as vue-cropperjs, vue-avatar, etc.

Taking vue-cropperjs as an example, you first need to install the library:

npm install vue-cropperjs --save

Then introduce and use the library in the Vue component:

<template>
  <div>
    <vue-cropper
      ref="cropper"
      :guides="true"
      :src="image"
      :aspect-ratio="1"
      :view-mode="1"
      @ready="onReady"
    ></vue-cropper>
    <button @click="cropImage">裁剪</button>
  </div>
</template>

<script>
import VueCropper from "vue-cropperjs";

export default {
  data() {
    return {
      image: "", // 原始图片
    };
  },
  components: {
    VueCropper,
  },
  methods: {
    onReady() {
      // 图片加载完成后的回调函数
    },
    cropImage() {
      const cropper = this.$refs.cropper.cropper; // 获取cropper实例
      const croppedCanvas = cropper.getCroppedCanvas(); // 获取裁剪后的canvas
      const croppedImage = croppedCanvas.toDataURL("image/png"); // 将canvas转换为base64格式的图片
      // 将裁剪后的图片进行保存或展示
    },
  },
};
</script>

In the above code, first Display the original image through the vue-cropper component, and configure the aspect ratio, view mode and other properties of the cropping box. Then after clicking the crop button, the cropped canvas object is obtained by calling the cropper method, and then converted into a base64 format image. Finally, the cropped image can be saved or displayed.

2. Picture rotation

Picture rotation refers to rotating the picture according to a certain angle, usually a multiple of 90 degrees. In Vue, you can use the transform attribute of CSS or the rotate method of canvas to achieve image rotation.

Take the transform attribute of css as an example. Suppose there is an img element that needs to be rotated 90 degrees counterclockwise:

<template>
  <div>
    <img ref="image" src="原始图片路径" alt="原始图片" />
    <button @click="rotateImage">旋转</button>
  </div>
</template>

<script>
export default {
  methods: {
    rotateImage() {
      const imageElement = this.$refs.image; // 获取img元素
      const currentRotation = parseInt(
        window.getComputedStyle(imageElement).getPropertyValue("transform").split("(")[1].split(")")[0]
      ); // 获取当前旋转角度
      const nextRotation = currentRotation - 90; // 逆时针旋转90度
      imageElement.style.transform = `rotate(${nextRotation}deg)`; // 设置旋转角度
    },
  },
};
</script>

In the above code, when the rotate button is clicked, the img is obtained by The transform attribute of the element, and then get the current rotation angle. Then subtract 90 degrees from the rotation angle, and then set the transform attribute of the element to achieve the effect of rotating the image 90 degrees counterclockwise.

Summary:

Dealing with image cropping and rotation problems encountered in Vue development can be achieved by using some open source image editing libraries. For image cropping, you can use libraries such as vue-cropperjs to achieve this. By obtaining the cropped canvas object, you can then convert it into a base64 format image for saving or displaying. For image rotation, you can use the transform attribute of CSS or the rotate method of canvas to achieve the image rotation effect by setting the rotation angle of the element.

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