• Android中Bitmap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

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

    2、Bitmap → byte[]

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

     3、byte[] → Bitmap

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

    4、Bitmap缩放

    Java代码 
    	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

    Java代码 
    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 

    Java代码 
    	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

    Java代码 
    	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

    Java代码 
    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

    Java代码 

     

    	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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  • 原文地址:https://www.cnblogs.com/qsl568/p/2400383.html
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