封面和内容拼图(也不知道官方的该怎么称呼这种图片,我这里就先称为内容拼图了)可以让我们对视频有大致的了解,在视频分享网站上很常见。今天说说怎么用FFmpeg+Java生成封面和内容拼图。

封面

FFmpeg截取封面非常简单,一个命令可以搞定:

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ffmpeg -i input.flv -ss 00:00:14.435 -vframes 1 out.png

参数解释:

  • -ss:时间字符串,指定截取时间点。如果指定的时间大于视频的最大时间,则没有输出。
  • -vframes 1:指定输出多少帧,这里就输出一帧

时间字符串的格式为[HH:]MM:SS[.m...]或者S+[.m...]。比如:55,12:03:45,23.189

内容拼图

QQ影音的剧情连拍功能就是内容拼图,可以指定图片的宽度和布局,然后按一定时间截取视频:

FFmpeg没法一个命令搞定内容拼图,我采用的方法是先让FFmpeg按固定时间截取图片保存到一个目录下,然后再用一段Java程序吧这些图片拼接起来。

相关命令:

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# 获取视频的时长,用于计算每秒截取几帧
ffprobe -v quiet -show_format -print_format json "inputFilePath"
# 按指定的fps截取视频,输出到指定位置下,输出文件名格式为:out001.png,out002.png...
ffmpeg -i "inputFilePath" -vf fps=1 out%3d.png

Java代码如下:

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/**
* 拼接多张图片文件到一张图片中
*
* @param files 用于拼图的图片文件列表
* @param width 输出拼图的宽度
* @param height 输出拼图的高度
* @param row 拼图的行数
* @param column 拼图的列数
* @param pageCount 指定输出几张拼图。如果小于等于0或者大于最大输出的张数,则为最大输出的张数
*/
public List<BufferedImage> mergeImageFiles(List<File> files, int width, int height, int row, int column, int pageCount) throws IOException {
if (width <= 0 || height <= 0) {
throw new IllegalArgumentException("wight/height is zero or negative");
}
if (column <= 0 || row <= 0) {
throw new IllegalArgumentException("column/row is zero or negative");
}
if (files == null) {
throw new IllegalArgumentException("image files is null or empty");
}
if (files.isEmpty()) {
return Lists.newArrayList(new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB));
}
List<BufferedImage> imageItemList = new ArrayList<>();
for (File file : files) {
BufferedImage image = ImageIO.read(file);
imageItemList.add(image);
}
return mergeImages(imageItemList, width, height, row, column, pageCount);
}
public List<BufferedImage> mergeImages(List<BufferedImage> images, int width, int height, int row, int column, int pageCount) throws IOException {
if (width <= 0 || height <= 0) {
throw new IllegalArgumentException("wight/height is zero or negative");
}
if (column <= 0 || row <= 0) {
throw new IllegalArgumentException("column/row is zero or negative");
}
if (images == null) {
throw new IllegalArgumentException("image files is null or empty");
}
if (images.isEmpty()) {
return Lists.newArrayList(new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB));
}
int pageImageCount = column * row;
int fullPageCount = (int) Math.ceil(images.size() / (double) pageImageCount);
if (pageCount <= 0 || pageCount > fullPageCount) {
pageCount = fullPageCount;
}
List<BufferedImage> pageList = new ArrayList<>(pageCount);
int partWidth = width / column;
int partHeight = height / row;
for (int pageIndex = 0; pageIndex < pageCount; pageIndex++) {
BufferedImage resultImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
Graphics2D graphics = resultImage.createGraphics();
for (int rowIndex = 0; rowIndex < row; rowIndex++) {
for (int columnIndex = 0; columnIndex < column; columnIndex++) {
int fileIndex = (pageIndex * pageImageCount) + (rowIndex * column) + columnIndex;
if (fileIndex >= images.size()) break;
BufferedImage partImage = images.get(fileIndex);
int currentPartWidth = partWidth;
int currentPartHeight = partHeight;
int currentDeltaX = 0;
int currentDeltaY = 0;
double widthScale = partImage.getWidth() / (double) partWidth;
double heightScale = partImage.getHeight() / (double) partHeight;
if (widthScale > heightScale) {
currentPartHeight = (int) (partImage.getHeight() / widthScale);
currentDeltaY = (partHeight - currentPartHeight) / 2;
} else {
currentPartWidth = (int) (partImage.getWidth() / heightScale);
currentDeltaX = (partWidth - currentPartWidth) / 2;
}
int currentX = columnIndex * partWidth + currentDeltaX;
int currentY = rowIndex * partHeight + currentDeltaY;
graphics.drawImage(partImage,
currentX, currentY, currentX + currentPartWidth, currentY + currentPartHeight,
0, 0, partImage.getWidth(), partImage.getHeight(),
null);
}
}
pageList.add(resultImage);
}
return pageList;
}

效果: