本文主要是介绍Android Drawable与Bitmap，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
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
1 Resources res = getResources(); 2 Bitmap bmp = BitmapFactory.decodeResource(res, R.drawable.icon);
2、Bitmap → byte[]
1 public byte[] Bitmap2Bytes(Bitmap bm) { 2 ByteArrayOutputStream baos = new ByteArrayOutputStream(); 3 bm.compress(Bitmap.CompressFormat.PNG, 100, baos); 4 return baos.toByteArray(); 5 }
3、byte[] → Bitmap
1 public Bitmap Bytes2Bimap(byte[] b) { 2 if (b.length != 0) { 3 return BitmapFactory.decodeByteArray(b, 0, b.length); 4 } else { 5 return null; 6 } 7 }
4、Bitmap缩放
1 public static Bitmap zoomBitmap(Bitmap bitmap, int width, int height) { 2 int w = bitmap.getWidth(); 3 int h = bitmap.getHeight(); 4 Matrix matrix = new Matrix(); 5 float scaleWidth = ((float) width / w); 6 float scaleHeight = ((float) height / h); 7 matrix.postScale(scaleWidth, scaleHeight); 8 Bitmap newbmp = Bitmap.createBitmap(bitmap, 0, 0, w, h, matrix, true); 9 return newbmp; 10 }
5、将Drawable转化为Bitmap
1 public static Bitmap drawableToBitmap(Drawable drawable) { 2 // 取 drawable 的长宽 3 int w = drawable.getIntrinsicWidth(); 4 int h = drawable.getIntrinsicHeight(); 5 6 // 取 drawable 的颜色格式 7 Bitmap.Config config = drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888 8 : Bitmap.Config.RGB_565; 9 // 建立对应 bitmap 10 Bitmap bitmap = Bitmap.createBitmap(w, h, config); 11 // 建立对应 bitmap 的画布 12 Canvas canvas = new Canvas(bitmap); 13 drawable.setBounds(0, 0, w, h); 14 // 把 drawable 内容画到画布中 15 drawable.draw(canvas); 16 return bitmap; 17 }
6、获得圆角图片
1 public static Bitmap getRoundedCornerBitmap(Bitmap bitmap, float roundPx) { 2 int w = bitmap.getWidth(); 3 int h = bitmap.getHeight(); 4 Bitmap output = Bitmap.createBitmap(w, h, Config.ARGB_8888); 5 Canvas canvas = new Canvas(output); 6 final int color = 0xff424242; 7 final Paint paint = new Paint(); 8 final Rect rect = new Rect(0, 0, w, h); 9 final RectF rectF = new RectF(rect); 10 paint.setAntiAlias(true); 11 canvas.drawARGB(0, 0, 0, 0); 12 paint.setColor(color); 13 canvas.drawRoundRect(rectF, roundPx, roundPx, paint); 14 paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN)); 15 canvas.drawBitmap(bitmap, rect, rect, paint); 16 17 return output; 18 }
7、获得带倒影的图片
1 public static Bitmap createReflectionImageWithOrigin(Bitmap bitmap) { 2 final int reflectionGap = 4; 3 int w = bitmap.getWidth(); 4 int h = bitmap.getHeight(); 5 6 Matrix matrix = new Matrix(); 7 matrix.preScale(1, -1); 8 9 Bitmap reflectionImage = Bitmap.createBitmap(bitmap, 0, h / 2, w, 10 h / 2, matrix, false); 11 12 Bitmap bitmapWithReflection = Bitmap.createBitmap(w, (h + h / 2), 13 Config.ARGB_8888); 14 15 Canvas canvas = new Canvas(bitmapWithReflection); 16 canvas.drawBitmap(bitmap, 0, 0, null); 17 Paint deafalutPaint = new Paint(); 18 canvas.drawRect(0, h, w, h + reflectionGap, deafalutPaint); 19 20 canvas.drawBitmap(reflectionImage, 0, h + reflectionGap, null); 21 22 Paint paint = new Paint(); 23 LinearGradient shader = new LinearGradient(0, bitmap.getHeight(), 0, 24 bitmapWithReflection.getHeight() + reflectionGap, 0x70ffffff, 25 0x00ffffff, TileMode.CLAMP); 26 paint.setShader(shader); 27 // Set the Transfer mode to be porter duff and destination in 28 paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN)); 29 // Draw a rectangle using the paint with our linear gradient 30 canvas.drawRect(0, h, w, bitmapWithReflection.getHeight() 31 + reflectionGap, paint); 32 33 return bitmapWithReflection; 34 }
三、Drawable
1、Bitmap转换成Drawable
1 Bitmap bm=xxx; //xxx根据你的情况获取 2 BitmapDrawable bd= new BitmapDrawable(getResource(), bm); 3 因为BtimapDrawable是Drawable的子类，最终直接使用bd对象即可。
2、Drawable缩放
1 public static Drawable zoomDrawable(Drawable drawable, int w, int h) { 2 int width = drawable.getIntrinsicWidth(); 3 int height = drawable.getIntrinsicHeight(); 4 // drawable转换成bitmap 5 Bitmap oldbmp = drawableToBitmap(drawable); 6 // 创建操作图片用的Matrix对象 7 Matrix matrix = new Matrix(); 8 // 计算缩放比例 9 float sx = ((float) w / width); 10 float sy = ((float) h / height); 11 // 设置缩放比例 12 matrix.postScale(sx, sy); 13 // 建立新的bitmap，其内容是对原bitmap的缩放后的图 14 Bitmap newbmp = Bitmap.createBitmap(oldbmp, 0, 0, width, height, 15 matrix, true); 16 return new BitmapDrawable(newbmp); 17 }
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