Android中Bitmap和Drawable

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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代码收藏代码

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

2、Bitmap → byte[]
Java代码收藏代码

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

3、byte[] → Bitmap
Java代码收藏代码

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

4、Bitmap缩放
Java代码收藏代码

 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代码收藏代码

  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代码收藏代码

  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代码收藏代码

  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代码收藏代码

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代码收藏代码

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);      }

本文转自的博客dyh7077063

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