Android中Bit地图和Drawable

一、相关概念

1、Drawable就是一个可画的对象，其可能是一张位图（BitmapDrawable），也可能是一个图形（ShapeDrawable），还有可能是一个图层（LayerDrawable），我们根据画图的需求，创建相应的可画对象

2、Canvas画布，绘图的目的区域，用于绘图

3、Bitmap位图，用于图的处理

4、Matrix矩阵

二、Bitmap

1、从资源中获取Bitmap

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

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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缩放

	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、将Drawable转化为Bitmap

public static Bitmap drawableToBitmap(Drawable drawable) {		// 取 drawable 的长宽		int w = drawable.getIntrinsicWidth();		int h = drawable.getIntrinsicHeight();		// 取 drawable 的颜色格式		Bitmap.Config config = drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888				: Bitmap.Config.RGB_565;		// 建立对应 bitmap		Bitmap bitmap = Bitmap.createBitmap(w, h, config);		// 建立对应 bitmap 的画布		Canvas canvas = new Canvas(bitmap);		drawable.setBounds(0, 0, w, h);		// 把 drawable 内容画到画布中		drawable.draw(canvas);		return bitmap;	}

6、获得圆角图片?

	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、获得带倒影的图片

	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转换成Drawable

Bitmap bm=xxx; //xxx根据你的情况获取BitmapDrawable bd= new BitmapDrawable(getResource(), bm); 因为BtimapDrawable是Drawable的子类，最终直接使用bd对象即可。

2、Drawable缩放

	public static Drawable zoomDrawable(Drawable drawable, int w, int h) {		int width = drawable.getIntrinsicWidth();		int height = drawable.getIntrinsicHeight();		// drawable转换成bitmap		Bitmap oldbmp = drawableToBitmap(drawable);		// 创建操作图片用的Matrix对象		Matrix matrix = new Matrix();		// 计算缩放比例		float sx = ((float) w / width);		float sy = ((float) h / height);		// 设置缩放比例		matrix.postScale(sx, sy);		// 建立新的bitmap，其内容是对原bitmap的缩放后的图		Bitmap newbmp = Bitmap.createBitmap(oldbmp, 0, 0, width, height,				matrix, true);		return new BitmapDrawable(newbmp);	}

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