Android Bitmap 图片处理

1.Bitmap，Drawable，InputStream，Byte[ ] 之间进行转换

/**
 * Drawable转化成Bitmap
 * @param drawable                      drawable
 * @return                              Bitmap
 */
public static Bitmap drawableToBitmap(Drawable drawable) {
    int intrinsicWidth = drawable.getIntrinsicWidth();
    int intrinsicHeight = drawable.getIntrinsicHeight();
    Bitmap.Config config = drawable.getOpacity() != PixelFormat.OPAQUE
            ? Bitmap.Config.ARGB_8888 : Bitmap.Config.RGB_565;
    Bitmap bitmap = Bitmap.createBitmap(intrinsicWidth, intrinsicHeight,config);
    Canvas canvas = new Canvas(bitmap);
    drawable.setBounds(0, 0, intrinsicWidth, intrinsicHeight);
    drawable.draw(canvas);
    return bitmap;
}

/**
 * Bitmap转换成Drawable
 * @param resources                     resources
 * @param bm                            bm
 * @return
 */
public static Drawable bitmapToDrawable(Resources resources, Bitmap bm) {
    Drawable drawable = new BitmapDrawable(resources, bm);
    return drawable;
}

/**
 * InputStream转换成Bitmap
 * @param is                            InputStream流
 * @return
 */
public static Bitmap bitmapToDrawable(InputStream is) {
    Bitmap bitmap = BitmapFactory.decodeStream(is);
    return bitmap;
}

2.Bitmap图片压缩

/**
 * 图片压缩
 * @param image                     image
 * @return
 */
public static Bitmap compressImage(Bitmap image) {
    if (image == null) {
        return null;
    }
    ByteArrayOutputStream bao = null;
    try {
        bao = new ByteArrayOutputStream();
        image.compress(Bitmap.CompressFormat.JPEG, 100, bao);
        byte[] bytes = bao.toByteArray();
        ByteArrayInputStream isBm = new ByteArrayInputStream(bytes);
        return BitmapFactory.decodeStream(isBm);
    } catch (OutOfMemoryError e) {
        e.printStackTrace();
    } finally {
        try {
            if (bao != null) {
                bao.close();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    return null;
}

3.将bitmap根据scale生成一张图片

/**
 * 将bitmap根据scale生成一张图片
 *
 * @param bitmap                    bitmap
 * @param scale                     等比缩放值
 * @return                          bitmap    
 */
public static Bitmap bitmapScale(Bitmap bitmap, float scale) {
    Matrix matrix = new Matrix();
    // 长和宽放大缩小的比例
    matrix.postScale(scale, scale);
    Bitmap resizeBmp = Bitmap.createBitmap(bitmap, 0, 0,
            bitmap.getWidth(), bitmap.getHeight(), matrix, true);
    return resizeBmp;
}

4.将View控件转换为bitmap

public static Bitmap convertViewToBitMap(View view){
    // 打开图像缓存
    view.setDrawingCacheEnabled(true);
    // 必须调用measure和layout方法才能成功保存可视组件的截图到png图像文件
    // 测量View大小
    int i = View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED);
    int n = View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED);
    view.measure(i, n);
    // 发送位置和尺寸到View及其所有的子View
    view.layout(0, 0, view.getMeasuredWidth(), view.getMeasuredHeight());
    // 获得可视组件的截图
    Bitmap bitmap = view.getDrawingCache();
    return bitmap;
}

/**
 * 该方法会报错，java.lang.IllegalArgumentException: width and height must be > 0
 */
public static Bitmap getBitmapFromView(View view){
    Bitmap returnedBitmap = Bitmap.createBitmap(view.getWidth(), view.getHeight(), Bitmap.Config.ARGB_8888);
    Canvas canvas = new Canvas(returnedBitmap);
    Drawable bgDrawable = view.getBackground();
    if (bgDrawable != null){
        bgDrawable.draw(canvas);
    } else{
        canvas.drawColor(Color.WHITE);
    }
    view.draw(canvas);
    return returnedBitmap;
}


//该方法验证可以
public static Bitmap loadBitmapFromView(View v) {
    v.measure(0, 0);
    int w = v.getMeasuredWidth();
    int h = v.getMeasuredHeight();
    if (w <= 0 || h <= 0) {
        DisplayMetrics metric = new DisplayMetrics();
        w = metric.widthPixels;// 屏幕宽度（像素）
        h = metric.heightPixels;// 屏幕高度（像素）
    }
    Bitmap bmp = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
    Canvas c = new Canvas(bmp);
    c.drawColor(Color.WHITE);
    //如果不设置canvas画布为白色，则生成透明
    v.layout(0, 0, w, h);
    v.draw(c);
    return bmp;
}

6.如何计算bitmap占用内存大小

• 如果图片要显示下Android设备上，ImageView最终是要加载Bitmap对象的，就要考虑单个Bitmap对象的内存占用了，如何计算一张图片的加载到内存的占用呢？其实就是所有像素的内存占用总和：
• bitmap内存大小 = 图片长度 x 图片宽度 x 单位像素占用的字节数
• 起决定因素就是最后那个参数了，Bitmap’常见有2种编码方式：ARGB_8888和RGB_565，ARGB_8888每个像素点4个byte，RGB_565是2个byte，一般都采用ARGB_8888这种。那么常见的1080*1920的图片内存占用就是：1920 x 1080 x 4 = 7.9M