Implement image filter effects in WeChat mini programs

Implementing picture filter effects in WeChat mini programs

With the popularity of social media applications, people are increasingly fond of applying filter effects to photos to Enhance the artistic effect and appeal of your photos. Picture filter effects can also be implemented in WeChat mini programs, providing users with more interesting and creative photo editing functions. This article will introduce how to implement image filter effects in WeChat mini programs and provide specific code examples.

First, we need to use the canvas component in the WeChat applet to load and edit images. The canvas component can draw images on the page and is a key element to achieve filter effects. The following is a simple canvas component example:

<canvas canvas-id="myCanvas" style="width: 100%; height: 100%;"></canvas>

Next, we need to write code in the js file of the applet to load and edit images. First, we need to get the context of the canvas component in order to draw images on the canvas. Then, we can use the drawImage method of canvas to load the image.

Page({
  onLoad: function() {
    var ctx = wx.createCanvasContext('myCanvas')

    wx.chooseImage({
      success: function(res) {
        var tempFilePaths = res.tempFilePaths

        ctx.drawImage(tempFilePaths[0], 0, 0, 300, 300)
        ctx.draw()
      }
    })
  }
})

In the above code, we use the wx.chooseImage method to select and load images. After selecting the image, we draw the image on the canvas. The ctx.drawImage method accepts the image path, x coordinate, y coordinate, and image width and height as parameters to determine the position and size of the image on the canvas. Finally, we call the ctx.draw method to draw the picture.

Now, we can start to implement the filter effect. The WeChat applet provides some filter effects for modifying the color of images. The following are some commonly used filter effect examples:

Page({
  onLoad: function() {
    var ctx = wx.createCanvasContext('myCanvas')

    wx.chooseImage({
      success: function(res) {
        var tempFilePaths = res.tempFilePaths

        ctx.drawImage(tempFilePaths[0], 0, 0, 300, 300)

        // 应用滤镜效果
        ctx.filter = 'grayscale(100%)' // 灰度滤镜
        ctx.filter = 'sepia(100%)' // 褐色滤镜
        ctx.filter = 'blur(5px)' // 模糊滤镜

        // 绘制滤镜后的图像
        ctx.drawImage(tempFilePaths[0], 0, 0, 300, 300)

        ctx.draw()
      }
    })
  }
})

In the above code, we apply the filter effect by setting ctx.filter. The grayscale filter can convert the image into a black and white grayscale image, the sepia filter can add an old photo-like effect to the image, and the blur filter can blur the image. When we use different filter effects, we only need to change the value of ctx.filter.

Finally, we can provide more filter effect options based on user choice. For example, add a selection box to the page that allows users to choose from different filter effects. The following is an example:

  <canvas canvas-id="myCanvas" style="width: 100%; height: 100%;"></canvas>
  选择滤镜

In the js file of the mini program, we added the changeFilter method to handle the filter effect selected by the user. The following is an example:

Page({
  data: {
    filterList: ['无', '灰度', '褐色', '模糊'],
    currentFilterIndex: 0
  },

  onLoad: function() {
    // ...
  },

  changeFilter: function(e) {
    var index = e.detail.value

    var filter = ''

    switch (index) {
      case '1':
        filter = 'grayscale(100%)'
        break
      case '2':
        filter = 'sepia(100%)'
        break
      case '3':
        filter = 'blur(5px)'
        break
      default:
        filter = ''
    }

    var ctx = wx.createCanvasContext('myCanvas')
    // ...

    ctx.filter = filter
    // ...
  }
})

In the above code, we use a data attribute to store the option list of filter effects and the currently selected filter index. When the user selects a different filter effect, the changeFilter method is triggered, in which ctx.filter is set according to the user's selection and the image is redrawn.

Through the above steps, we have implemented the function of applying image filter effects in WeChat applet. Users can choose different filter effects to edit and beautify photos, adding more fun and creativity to WeChat mini programs.

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