短视频系统源码，如何限制视频分辨率？

导言：

在短视频系统源码的许多场景下，我们需要确保用户上传的视频满足一定的分辨率要求，以保证在后续的处理中能够获得良好的视觉效果。在短视频系统源码开发时需要对用户上传的视频分辨率进行限制，以确保页面加载和播放的性能。

技术实现步骤：

1、创建视频元素和 Canvas：

const video = document.createElement('video');
const canvas = document.createElement('canvas');
const context = canvas.getContext('2d');

2、加载视频文件

video.preload = 'metadata';
video.src = URL.createObjectURL(videoFile);

3、获取视频元数据

video.onloadedmetadata = () => {
  const videoWidth = video.videoWidth;
  const videoHeight = video.videoHeight;

  // 进行分辨率校验...
};

4.分辨率校验逻辑：

// 校验最小分辨率
if (minResolution && (videoWidth < minResolution[0] || videoHeight < minResolution[1])) {
  reject(`分辨率太小，最小要求 ${minResolution[0]}x${minResolution[1]}`);
  return;
}

// 校验最大分辨率
if (maxResolution && (videoWidth > maxResolution[0] || videoHeight > maxResolution[1])) {
  reject(`分辨率太大，最大允许 ${maxResolution[0]}x${maxResolution[1]}`);
  return;
}

// 通过校验
resolve(true);

5、异常处理：

video.onerror = () => {
  reject('无法读取视频信息');
};

6、使用 Canvas 提取视频帧：

video.onloadeddata = () => {
  canvas.width = video.videoWidth;
  canvas.height = video.videoHeight;
  context.drawImage(video, 0, 0, canvas.width, canvas.height);
};

4. 示例用法：

const videoFile: File = /* 从文件输入获取的 File 对象 */;
const minResolution: Resolution = [640, 480];
const maxResolution: Resolution = [1920, 1080];

validateResolutionInBrowser(videoFile, minResolution, maxResolution)
  .then((isValid: boolean) => {
    console.log(isValid ? '分辨率符合要求' : '分辨率不符合要求');
  })
  .catch((error: string) => {
    console.error(`校验失败: ${error}`);
  });

完整代码

type Resolution = [number, number];

function validateResolutionInBrowser(videoFile: File, minResolution?: Resolution, maxResolution?: Resolution): Promise<boolean> {
  return new Promise((resolve, reject) => {
    const video = document.createElement('video');
    const canvas = document.createElement('canvas');
    const context = canvas.getContext('2d');

    video.preload = 'metadata';
    video.src = URL.createObjectURL(videoFile);

    video.onloadedmetadata = () => {
      const videoWidth = video.videoWidth;
      const videoHeight = video.videoHeight;

      // 校验最小分辨率
      if (minResolution && (videoWidth < minResolution[0] || videoHeight < minResolution[1])) {
        reject(`分辨率太小，最小要求 ${minResolution[0]}x${minResolution[1]}`);
        return;
      }

      // 校验最大分辨率
      if (maxResolution && (videoWidth > maxResolution[0] || videoHeight > maxResolution[1])) {
        reject(`分辨率太大，最大允许 ${maxResolution[0]}x${maxResolution[1]}`);
        return;
      }

      // 通过校验
      resolve(true);
    };

    video.onerror = () => {
      reject('无法读取视频信息');
    };

    video.onloadeddata = () => {
      // 使用 Canvas 提取视频帧
      canvas.width = video.videoWidth;
      canvas.height = video.videoHeight;
      context.drawImage(video, 0, 0, canvas.width, canvas.height);
    };
  });
}

// 示例用法：
const videoFile: File = /* 从文件输入获取的 File 对象 */;
const minResolution: Resolution = [640, 480];
const maxResolution: Resolution = [1920, 1080];

validateResolutionInBrowser(videoFile, minResolution, maxResolution)
  .then((isValid: boolean) => {
    console.log(isValid ? '分辨率符合要求' : '分辨率不符合要求');
  })
  .catch((error: string) => {
    console.error(`校验失败: ${error}`);
  });