Android 缩略图

第一种方法 /** * 当图片超过手机屏幕尺寸 * 宽度和高度进行一半缩放 * @param res * @param id * @param opts

第一种方法

/**     * 当图片超过手机屏幕尺寸     * 宽度和高度进行一半缩放     * @param res     * @param id     * @param opts     * @return     */    public Bitmap DecodeFileBitmap(Resources res, int id, Options opts){    	BitmapFactory.Options o = new BitmapFactory.Options();    	o.inJustDecodeBounds = true;    	BitmapFactory.decodeResource(res, id, o);    	final int REQUIRED_HEIGHT = screenheight; //800        final int REQUIRED_WIDTH = screenwidth; //480        int width_tmp = o.outWidth,height_tmp = o.outHeight;        System.out.println("source"+"weight"+width_tmp + "  " + "source height"+height_tmp);                int scale = 1;        while(true){        	if (width_tmp / 2 < REQUIRED_WIDTH                    && height_tmp / 2 < REQUIRED_HEIGHT)                break;            width_tmp /= 2;            height_tmp /= 2;            scale++;        	Log.w("===", scale + "''" + width_tmp + "  " + height_tmp);        }        BitmapFactory.Options o2 = new BitmapFactory.Options();        o2.inSampleSize = scale;        return BitmapFactory.decodeResource(res,id,o2);    }

第二种方法：

/**     * 此根据输入的宽和高来定制缩放比例     * @param res     * @param id     * @return     */    public Bitmap DecodeFileBitmap(Resources res, int id){    	BitmapFactory.Options op = new BitmapFactory.Options();    	op.inJustDecodeBounds = true;    	Bitmap bmp = BitmapFactory.decodeResource(res, id, op);    	    	int wRatio = (int)Math.ceil(op.outWidth/200);    	int hRatio = (int)Math.ceil(op.outHeight/200);    	    	System.out.println("wRatio"+wRatio +"/n"+"hRatio"+hRatio);    	    	if(wRatio > 1 && hRatio > 1){    		if(wRatio > hRatio){    			op.inSampleSize = wRatio;    		}else{    			op.inSampleSize = hRatio;    		}    	}    	op.inJustDecodeBounds = false;    	bmp = BitmapFactory.decodeResource(res, id, op);    	System.out.println("BMP Width"+bmp.getWidth()+"/n"+"BMP Height"+bmp.getHeight());    	return bmp;    }

第三种：Android自带工具类

/**     * 利用android工具类来对图片以中心点进行缩放     *(此缩放会产生局部周边景物损失，起保证中心点图片完整)     * @param res     * @param id     * @return BitMap图片     */    public Bitmap decodebitmapunit(Resources res, int id){    	Bitmap source = BitmapFactory.decodeResource(res, id);//    	source = ThumbnailUtils.extractThumbnail(source, 200, 200, 0|ThumbnailUtils.OPTIONS_RECYCLE_INPUT);//    	source = ThumbnailUtils.extractThumbnail(source, 50, 50);    	source = ImageZoom.extractThumbnail(source, 200,200);    	return source;    }

工具类：

package com.play.image;import android.graphics.Bitmap;import android.graphics.Canvas;import android.graphics.Matrix;import android.graphics.Rect;class ImageZoom {	private static final int OPTIONS_SCALE_UP = 0x1;	public static final int OPTIONS_RECYCLE_INPUT = 0x2;	private static final int OPTIONS_NONE = 0x0;	public static Bitmap extractThumbnail(Bitmap source, int width, int height)	{		return extractThumbnail(source, width, height, OPTIONS_NONE);	}	private static Bitmap extractThumbnail(Bitmap source, int width,			int height, int options) {		if (source == null) {			return null;		}		float scale;		if (source.getWidth() < source.getHeight()) {			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,				OPTIONS_SCALE_UP | options);		return thumbnail;	}	private static Bitmap transform(Matrix scaler, Bitmap source,			int targetWidth, int targetHeight, int options) {		boolean scaleUp = (options & OPTIONS_SCALE_UP) != 0;		boolean recycle = (options & OPTIONS_RECYCLE_INPUT) != 0;		int deltaX = source.getWidth() - targetWidth;		int deltaY = source.getHeight() - targetHeight;		if (!scaleUp && (deltaX < 0 || deltaY < 0)) {			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();			}			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) {			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;	}}

ThumbnailUtils.java 源码：

. http://www.oschina.net/code/explore/android-2.2-froyo/android/media/ThumbnailUtils.java .

所以本人把2.2版本的SDK的android.media.*包下的类ThumbnailUtils.java、DecoderCapabilities.java、ExifInterface.java、MediaFile.java、MediaMetadataRetriever.java五个类源码放到我的项目里，使用 ThumbnailUtils.createVideoThumbnail(imageUrl, ThumbnailUtils.OPTIONS_RECYCLE_INPUT);方法在Google Nexus S手机上能获取到网络视频缩略图（不管是别的手机拍的还是自己的手机拍的都可以），而使用索爱X8 e151、MOTO ME811和三星I9100都不能获取网络视频缩略图，这是为什么呢？求帮助。