Android进阶篇Bitmap操作类

/**
 * @author gongchaobin
 *
 * Bitmap工具类
 */
public class BitmapUtil {
    
    /** 
    * 以最省内存的方式读取本地资源的图片 或者SDCard中的图片
    * 
    * @param imagePath  图片在SDCard中的路径
    * @return 
    */
    public static Bitmap getSDCardImg(String imagePath){
        BitmapFactory.Options opt = new BitmapFactory.Options();
        opt.inPreferredConfig = Bitmap.Config.RGB_565;
        opt.inPurgeable = true;
        opt.inInputShareable = true;
        //获取资源图片 
        return BitmapFactory.decodeFile(imagePath, opt);
    }
    
    /**
     * 读取SD卡图片(以流的形式,减少内存的消耗)
     * 
     * @param context 上下文
     * @param resId 图片的ID 
     * @return
     */
    public static Bitmap readBitMap(Context context, int resId) {
        BitmapFactory.Options opt = new BitmapFactory.Options();
        opt.inPreferredConfig = Bitmap.Config.RGB_565;
        opt.inPurgeable = true;
        opt.inInputShareable = true;
        InputStream is = context.getResources().openRawResource(resId);
        return BitmapFactory.decodeStream(is, null, opt);
    }
    
    /**
     * 按比例对图片进行缩放(防止内存溢出)
     * 
     * @param path 图片的存储路径
     * @param width 
     * @param height
     * @return
     */
    public static Bitmap getBitmapFromFile(String path, int width, int height) {
        BitmapFactory.Options opts = null;
        if (width > 0 && height > 0) {
            opts = new BitmapFactory.Options();
            opts.inPreferredConfig = Bitmap.Config.RGB_565;
            //不分配内存
            opts.inJustDecodeBounds = true;
            BitmapFactory.decodeFile(path, opts);
            // 计算图片缩放比例
            opts.inSampleSize = computeSampleSize(opts,-1,128*128);
            opts.inJustDecodeBounds = false;
            opts.inInputShareable = true;
            opts.inPurgeable = true;
        }
        try {
            return BitmapFactory.decodeFile(path, opts);
        } catch (OutOfMemoryError e) {
            e.printStackTrace();
        }
        return null;
    }
    
    /**
     * Android提供计算inSampleSize的方法
     */
    public static int computeSampleSize(BitmapFactory.Options options,int minSideLength, int maxNumOfPixels) {
        int initialSize = computeInitialSampleSize(options, minSideLength,maxNumOfPixels);
        int roundedSize;
        if (initialSize <= 8) {
            roundedSize = 1;
            while (roundedSize < initialSize) {
                roundedSize <<= 1;
            }
        } else {
            roundedSize = (initialSize + 7) / 8 * 8;
        }
        return roundedSize;
    }
     
    private static int computeInitialSampleSize(BitmapFactory.Options options,int minSideLength, int maxNumOfPixels) {
        double w = options.outWidth;
        double h = options.outHeight;
     
        int lowerBound = (maxNumOfPixels == -1) ? 1 :(int) Math.ceil(Math.sqrt(w * h / maxNumOfPixels));
        int upperBound = (minSideLength == -1) ? 128 :(int) Math.min(Math.floor(w / minSideLength),Math.floor(h / minSideLength));
     
        if (upperBound < lowerBound) {
            return lowerBound;
        }
     
        if ((maxNumOfPixels == -1) && (minSideLength == -1)) {
            return 1;
        } else if (minSideLength == -1) {
            return lowerBound;
        } else {
            return upperBound;
        }
    }   
    
    /**
     * 生成圆角图片
     * 
     * @param bitmap 资源位图
     * @param pixels 圆角弧度
     * @return Bitmap 
     */
    public static Bitmap getRoundedCornerBitmap(Bitmap bitmap,int pixels){
        try {
            Bitmap output = Bitmap.createBitmap(bitmap.getWidth(),bitmap.getHeight(), Config.ARGB_8888);
            Canvas canvas = new Canvas(output);     
            Paint paint = new Paint();
            Rect rect = new Rect(0, 0, bitmap.getWidth(),bitmap.getHeight());  
            RectF rectF = new RectF(new Rect(0, 0, bitmap.getWidth(),bitmap.getHeight()));
            float roundPx = pixels;
            paint.setAntiAlias(true);
            canvas.drawARGB(0, 0, 0, 0);
            paint.setColor(Color.BLACK);  
            canvas.drawRoundRect(rectF, roundPx, roundPx, paint);
            paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));    
            Rect src = new Rect(0, 0, bitmap.getWidth(),bitmap.getHeight());
            canvas.drawBitmap(bitmap, src, rect, paint); 
            return output;
        } catch (Exception e) {   
            return bitmap;
        }
    }
    
    /**
     * 图片反转
     * 
     * @param path 图片的路径
     * @param angle 旋转的角度
     */
    public static Bitmap reverseBitmap(String path,float angle){
        //图片太大 要进行防止OOM操作
        Bitmap bitmap = BitmapFactory.decodeFile(path);
        Matrix m = new Matrix();  
        int width = bitmap.getWidth();  
        int height = bitmap.getHeight();  
        m.setRotate(angle);
        bitmap = Bitmap.createBitmap(bitmap, 0, 0, width, height,m, true);
        return bitmap;
    }
    
    /**
     * 图片旋转并进行缩放(缩放用来适应显示区域)
     * 
     * @param bitmap 原图
     * @param count 旋转的count
     * @return Bitmap
     */
    @SuppressWarnings("unused")
    private Bitmap reverseAndZoomBitmap(Bitmap bitmap,int count){
        Matrix  matrix = new Matrix();
        int width = bitmap.getWidth();
        int height = bitmap.getHeight();
        if(count == 0 || count == 4){
            matrix.setRotate(90*count);
        }else {
            matrix.setRotate(90*count);
            float scale = (float)height/width;
            matrix.postScale(scale, scale);
        }
        return Bitmap.createBitmap(bitmap, 0, 0, width, height,matrix, true);
    }
    
    /**
     * 回收Bitmap对象
     * 
     * @param bitmap 需要回收的Bitmap对象
     */
    public static void recyleBitmap(Bitmap bitmap){
        if(bitmap != null && !bitmap.isRecycled()){
            bitmap.recycle();
            System.gc();
        }
    }
}