drawable與bitmap

1、Drawable就是一個可畫的對象，其可能是一張位圖（BitmapDrawable），也可能是一個圖形（ShapeDrawable），還有可能是一個圖層（LayerDrawable），我們根據畫圖的需求，創建相應的可畫對象

2、Canvas畫布，繪圖的目的區域，用於繪圖

3、Bitmap位圖，用於圖的處理

4、Matrix矩陣

二、Bitmap

1、從資源中獲取Bitmap

		Resources res = getResources();
		Bitmap bmp = BitmapFactory.decodeResource(res, R.drawable.icon);

2、Bitmap → byte[]

	public byte[] Bitmap2Bytes(Bitmap bm) {
		ByteArrayOutputStream baos = new ByteArrayOutputStream();
		bm.compress(Bitmap.CompressFormat.PNG, 100, baos);
		return baos.toByteArray();
	}

 3、byte[] → Bitmap

	public Bitmap Bytes2Bimap(byte[] b) {
		if (b.length != 0) {
			return BitmapFactory.decodeByteArray(b, 0, b.length);
		} else {
			return null;
		}
	}

  4、Bitmap縮放

 

	public static Bitmap zoomBitmap(Bitmap bitmap, int width, int height) {
		int w = bitmap.getWidth();
		int h = bitmap.getHeight();
		Matrix matrix = new Matrix();
		float scaleWidth = ((float) width / w);
		float scaleHeight = ((float) height / h);
		matrix.postScale(scaleWidth, scaleHeight);
		Bitmap newbmp = Bitmap.createBitmap(bitmap, 0, 0, w, h, matrix, true);
		return newbmp;
	}

  5、將Drawable轉化爲Bitmap

public static Bitmap drawableToBitmap(Drawable drawable) {
		// 取 drawable 的長寬
		int w = drawable.getIntrinsicWidth();
		int h = drawable.getIntrinsicHeight();

		// 取 drawable 的顏色格式
		Bitmap.Config config = drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888
				: Bitmap.Config.RGB_565;
		// 建立對應 bitmap
		Bitmap bitmap = Bitmap.createBitmap(w, h, config);
		// 建立對應 bitmap 的畫布
		Canvas canvas = new Canvas(bitmap);
		drawable.setBounds(0, 0, w, h);
		// 把 drawable 內容畫到畫布中
		drawable.draw(canvas);
		return bitmap;
	}

6、獲得圓角圖片 

	public static Bitmap getRoundedCornerBitmap(Bitmap bitmap, float roundPx) {
		int w = bitmap.getWidth();
		int h = bitmap.getHeight();
		Bitmap output = Bitmap.createBitmap(w, h, Config.ARGB_8888);
		Canvas canvas = new Canvas(output);
		final int color = 0xff424242;
		final Paint paint = new Paint();
		final Rect rect = new Rect(0, 0, w, h);
		final RectF rectF = new RectF(rect);
		paint.setAntiAlias(true);
		canvas.drawARGB(0, 0, 0, 0);
		paint.setColor(color);
		canvas.drawRoundRect(rectF, roundPx, roundPx, paint);
		paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
		canvas.drawBitmap(bitmap, rect, rect, paint);

		return output;
	}

 

 7、獲得帶倒影的圖片

	public static Bitmap createReflectionImageWithOrigin(Bitmap bitmap) {
		final int reflectionGap = 4;
		int w = bitmap.getWidth();
		int h = bitmap.getHeight();

		Matrix matrix = new Matrix();
		matrix.preScale(1, -1);

		Bitmap reflectionImage = Bitmap.createBitmap(bitmap, 0, h / 2, w,
				h / 2, matrix, false);

		Bitmap bitmapWithReflection = Bitmap.createBitmap(w, (h + h / 2),
				Config.ARGB_8888);

		Canvas canvas = new Canvas(bitmapWithReflection);
		canvas.drawBitmap(bitmap, 0, 0, null);
		Paint deafalutPaint = new Paint();
		canvas.drawRect(0, h, w, h + reflectionGap, deafalutPaint);

		canvas.drawBitmap(reflectionImage, 0, h + reflectionGap, null);

		Paint paint = new Paint();
		LinearGradient shader = new LinearGradient(0, bitmap.getHeight(), 0,
				bitmapWithReflection.getHeight() + reflectionGap, 0x70ffffff,
				0x00ffffff, TileMode.CLAMP);
		paint.setShader(shader);
		// Set the Transfer mode to be porter duff and destination in
		paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));
		// Draw a rectangle using the paint with our linear gradient
		canvas.drawRect(0, h, w, bitmapWithReflection.getHeight()
				+ reflectionGap, paint);

		return bitmapWithReflection;
	}

 三、Drawable

1、Bitmap轉換成Drawable

Bitmap bm=xxx; //xxx根據你的情況獲取
BitmapDrawable bd= new BitmapDrawable(getResource(), bm); 
因爲BtimapDrawable是Drawable的子類，最終直接使用bd對象即可。

2、Drawable縮放

	public static Drawable zoomDrawable(Drawable drawable, int w, int h) {
		int width = drawable.getIntrinsicWidth();
		int height = drawable.getIntrinsicHeight();
		// drawable轉換成bitmap
		Bitmap oldbmp = drawableToBitmap(drawable);
		// 創建操作圖片用的Matrix對象
		Matrix matrix = new Matrix();
		// 計算縮放比例
		float sx = ((float) w / width);
		float sy = ((float) h / height);
		// 設置縮放比例
		matrix.postScale(sx, sy);
		// 建立新的bitmap，其內容是對原bitmap的縮放後的圖
		Bitmap newbmp = Bitmap.createBitmap(oldbmp, 0, 0, width, height,
				matrix, true);
		return new BitmapDrawable(newbmp);
	}

3、犧牲圖片質量爲代價，將圖片進行放縮

BitmapFactory.Options opts = new BitmapFactory.Options();
opts.inJustDecodeBounds = true;
Bitmap bitmap = BitmapFactory.decodeFile(imageFile, opts);

設置inJustDecodeBounds爲true後，decodeFile並不分配空間，但可計算出原始圖片的長度和寬度，即opts.width和opts.height。有了這兩個參數，再通過一定的算法，即可得到一個恰當的inSampleSize。Android提供了一種動態計算的方法。如下：

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;
    }
}   

我們只需要使用此函數就行了：

BitmapFactory.Options opts = new BitmapFactory.Options();
opts.inJustDecodeBounds = true;
BitmapFactory.decodeFile(imageFile, opts);
             
opts.inSampleSize = computeSampleSize(opts, -1, 128*128);
//這裏一定要將其設置回false，因爲之前我們將其設置成了true      
opts.inJustDecodeBounds = false;
try {
    Bitmap bmp = BitmapFactory.decodeFile(imageFile, opts);
    imageView.setImageBitmap(bmp);
    } catch (OutOfMemoryError err) {
    }

4、創建臨時空間

當在android設備中載入較大圖片資源時，可以創建一些臨時空間，將載入的資源載入到臨時空間中。

BitmapFactory.Options bfOptions=new BitmapFactory.Options();
             bfOptions.inDither=false;                    
             bfOptions.inPurgeable=true;              
             bfOptions.inTempStorage=new byte[12 * 1024]; 
            // bfOptions.inJustDecodeBounds = true;
             File file = new File(pePicFile.getAbsolutePath() + "/"+info.getImage());
             FileInputStream fs=null;
             try {
                fs = new FileInputStream(file);
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            }
             Bitmap bmp = null;
             if(fs != null)
                try {
                    bmp = BitmapFactory.decodeFileDescriptor(fs.getFD(), null, bfOptions);
                } catch (IOException e) {
                    e.printStackTrace();
                }finally{ 
                    if(fs!=null) {
                        try {
                            fs.close();
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }
                }