微信小程序内图片压缩方法

AI助手支持GPT4.0

//*************** 图片压缩 ***********
// 判断图片大小是否满足需求
function imageSizeIsLessLimitSize(imagePath, limitSize, lessCallBack, moreCallBack) {
  wx.getFileInfo({
      filePath: imagePath,
      success(res) {
          if (res.size > 1024 * limitSize) {
              moreCallBack();
          } else {
              lessCallBack();
          }
      }
  })
};
/**
* 获取画布图片 
*/
// 利用cavas进行压缩  每次压缩都需要ctx.draw()  wx.canvasToTempFilePath()连用
function getCanvasImage(canvasId, imagePath, imageW, imageH, getImgsuccess) {
  const ctx = wx.createCanvasContext(canvasId);
  ctx.drawImage(imagePath, 0, 0, imageW, imageH);
  ctx.draw(false, setTimeout(function() { // 一定要加定时器，因为ctx.draw()应用到canvas是有个时间的
      wx.canvasToTempFilePath({
          canvasId: canvasId,
          x: 0,
          y: 0,
          width: imageW,
          height: imageH,
          quality: 1,
          success: function(res) {
              getImgsuccess(res.tempFilePath);
          },
      });
  }, 200));
};

// 主调用方法

/**
* 获取小于限制大小的Image, limitSize默认为100KB，递归调用。
*/
function getLessLimitSizeImage(canvasId, imagePath, limitSize = 100, drawWidth, callBack) {
  imageSizeIsLessLimitSize(imagePath, limitSize,
      (lessRes) => {
          callBack(imagePath);
      },
      (moreRes) => {
          console.log('压缩图片');
          wx.getImageInfo({
              src: imagePath,
              success: function(imageInfo) {
                  var maxSide = Math.max(imageInfo.width, imageInfo.height);
                  //画板的宽高默认是windowWidth
                  var windowW = drawWidth;
                  var scale = 1;
                  if (maxSide > windowW) {
                      scale = windowW / maxSide;
                  }
                  var imageW = Math.trunc(imageInfo.width * scale);
                  var imageH = Math.trunc(imageInfo.height * scale);
                  console.log('调用压缩', imageW, imageH);
                  getCanvasImage(canvasId, imagePath, imageW, imageH,
                      (pressImgPath) => {
                          console.log(pressImgPath)
                          getLessLimitSizeImage(canvasId, pressImgPath, limitSize, drawWidth * 0.95, callBack);
                      }
                  );
              }
          })
      }
  )
};
// 图片转basee64    io操作 使用异步方式
function getBase64(img) {
  return new Promise(function(resolve, reject) {
      const FSM = wx.getFileSystemManager();
      FSM.readFile({
          filePath: img,
          encoding: 'base64',
          success(data) {
              resolve(data)
          }
      })
  })
}

export { getLessLimitSizeImage, imageSizeIsLessLimitSize, getCanvasImage, getBase64 }