搭建直播平台，android 如何得到本地视频的缩略图
public class VideoThumbUtils {
/**
* 得到视屏的缩略图
*
* @param videoPath
* @param width
* @param height
* @return
*/
public static Bitmap getVideoThumbnail(String videoPath, int width, int height) {
Bitmap result = null;
Bitmap temp = null;
if(videoPath==null){
return null;
}
File file = new File(videoPath);
if (!file.exists()) {
return null;
}
MediaMetadataRetriever metadataRetriever = new MediaMetadataRetriever();
try {
metadataRetriever.setDataSource(videoPath); // 设置视屏资源（还有一种是传url的，这里传的string）
String time = metadataRetriever.extractMetadata(MediaMetadataRetriever.METADATA_KEY_DURATION);
long frameTime = Long.parseLong(time) * 1000 / 2;// 视屏前面的帧可能为黑屏，所以取中间的帧
temp = metadataRetriever.getFrameAtTime(frameTime, MediaMetadataRetriever.OPTION_CLOSEST_SYNC);
if (null == temp) {
temp = metadataRetriever.getFrameAtTime(0);
}
} catch (Exception o) {
o.printStackTrace();
} finally {
try {
metadataRetriever.release();
} catch (RuntimeException o) {
o.printStackTrace();
}
}
result = extractThumbnail(temp, width, height, ThumbnailUtils.OPTIONS_RECYCLE_INPUT); //对得到的bitmap压缩
return result;
}
private static Bitmap extractThumbnail(Bitmap source, int width, int height,
int options) {
if (source == null) {
return null;
}
float scale;
if (source.getWidth() < source.getHeight()) { //得到压缩比
scale = width / (float) source.getWidth();
} else {
scale = height / (float) source.getHeight();
}
Matrix matrix = new Matrix();
matrix.setScale(scale, scale);
Bitmap thumbnail = transform(matrix, source, width, height,
0x1 | options);
return thumbnail;
}
private static Bitmap transform(Matrix scaler, Bitmap source, int targetWidth,
int targetHeight, int options) {
boolean scaleUp = (options & 0x1) != 0;
boolean recycle = (options & ThumbnailUtils.OPTIONS_RECYCLE_INPUT) != 0;
int deltaX = source.getWidth() - targetWidth;
int deltaY = source.getHeight() - targetHeight;
if (!scaleUp && (deltaX < 0 || deltaY < 0)) {
/*
* In such case the bitmap is smaller, at least in one dimension, than the target. Transform
* it by placing as much of the image as possible into the target and leaving the top/bottom
* or left/right (or both) black.
*/
Bitmap b2 = Bitmap.createBitmap(targetWidth, targetHeight,
Bitmap.Config.ARGB_8888);
Canvas c = new Canvas(b2);
int deltaXHalf = Math.max(0, deltaX / 2);
int deltaYHalf = Math.max(0, deltaY / 2);
Rect src = new Rect(deltaXHalf, deltaYHalf, deltaXHalf
+ Math.min(targetWidth, source.getWidth()), deltaYHalf
+ Math.min(targetHeight, source.getHeight()));
int dstX = (targetWidth - src.width()) / 2;
int dstY = (targetHeight - src.height()) / 2;
Rect dst = new Rect(dstX, dstY, targetWidth - dstX, targetHeight
- dstY);
c.drawBitmap(source, src, dst, null);
if (recycle) {
source.recycle();
}
c.setBitmap(null);
return b2;
}
float bitmapWidthF = source.getWidth();
float bitmapHeightF = source.getHeight();
float bitmapAspect = bitmapWidthF / bitmapHeightF;
float viewAspect = (float) targetWidth / targetHeight;
if (bitmapAspect > viewAspect) {
float scale = targetHeight / bitmapHeightF;
if (scale < .9F || scale > 1F) {
scaler.setScale(scale, scale);
} else {
scaler = null;
}
} else {
float scale = targetWidth / bitmapWidthF;
if (scale < .9F || scale > 1F) {
scaler.setScale(scale, scale);
} else {
scaler = null;
}
}
Bitmap b1;
if (scaler != null) {
// used for minithumb and crop, so we want to filter here.
b1 = Bitmap.createBitmap(source, 0, 0, source.getWidth(),
source.getHeight(), scaler, true);
} else {
b1 = source;
}
if (recycle && b1 != source) {
source.recycle();
}
int dx1 = Math.max(0, b1.getWidth() - targetWidth);
int dy1 = Math.max(0, b1.getHeight() - targetHeight);
Bitmap b2 = Bitmap.createBitmap(b1, dx1 / 2, dy1 / 2, targetWidth,
targetHeight);
if (b2 != b1) {
if (recycle || b1 != source) {
b1.recycle();
}
}
return b2;
}
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