微信小程序checkbox样式和background修改

/*checkbox 整体大小  */
checkbox {
    width: 34rpx;
    height: 34rpx;
    margin-top:7.5rpx;
    margin-right:24rpx;
  }
  /*checkbox 选项框大小  */
  checkbox .wx-checkbox-input {
    width: 34rpx;
    height: 34rpx;
  }
  /*checkbox选中后样式  */
  checkbox .wx-checkbox-input.wx-checkbox-input-checked {
    background-image: url("data:image/png;base64,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");
    background-size: 100% 100%;
    background-repeat: no-repeat;
  }
  /*checkbox选中后图标样式  */
  checkbox .wx-checkbox-input.wx-checkbox-input-checked::before {
    width: 28rpx;
    height: 28rpx;
    line-height: 28rpx;
    text-align: center;
    font-size: 22rpx;
    color: #fff;
    background-image: url("data:image/png;base64,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");
    transform: translate(-50%, -50%) scale(1);
    -webkit-transform: translate(-50%, -50%) scale(1);
  }