Android缩放drawable

http://blog.sina.com.cn/s/blog_4a88cf5001011nu1.html

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，绘制的目的区域，用于绘图

3.       Bitmap位图，用于图的处理

4.       Matrix矩阵，此例中用于操作图片

二、 步骤

1.       把drawable画到位图对象上

2.       对位图对象做缩放（或旋转等）操作

3.       把位图再转换成drawable

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

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

四、其它

import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.PixelFormat;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.graphics.RectF;
import android.graphics.Bitmap.Config;
import android.graphics.PorterDuff.Mode;
import android.graphics.drawable.Drawable;

public class FunctionUtil {

 
 public static Bitmap imageScale(Bitmap bitmap,int dst_w, int dst_h){
  
  int  src_w =bitmap.getWidth();
  int  src_h =bitmap.getHeight();
  float scale_w= ((float)dst_w)/src_w;
  float  scale_h= ((float)dst_h)/src_h;
  Matrix  matrix= new Matrix();
  matrix.postScale(scale_w,scale_h);
  Bitmap dstbmp =Bitmap.createBitmap(bitmap, 0, 0, src_w, src_h, matrix,true);
  
  return dstbmp;
 }

或者使用Bitmap.createScaledBitmap(bitmap, width, heigth,true);方法，

需要指定缩放后的图片大小尺寸。

 
 
 public static Bitmap drawabletoBitmap(Drawabledrawable){
  
  int width =drawable.getIntrinsicWidth();
  int height =drawable.getIntrinsicWidth();
  
  Bitmap bitmap =Bitmap.createBitmap(width, height, drawable.getOpacity() !=PixelFormat.OPAQUE ?
     Bitmap.Config.ARGB_8888: Bitmap.Config.RGB_565);
  Canvas canvas = newCanvas(bitmap);
  drawable.setBounds(0, 0, width,height);
  
  drawable.draw(canvas);
  
  return bitmap;
 }
 
 
 public static Bitmap getRCB(Bitmap bitmap, floatroundPX) //RCB means Rounded Corner Bitmap
 {
  Bitmap dstbmp =Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(),Config.ARGB_8888);
  Canvas canvas = newCanvas(dstbmp);
  
  final int color =0xff424242;
  final Paint paint = newPaint();
  final Rect rect = new Rect(0,0, bitmap.getWidth(), bitmap.getHeight());
  final RectF rectF = newRectF(rect);
  paint.setAntiAlias(true);
  canvas.drawARGB(0, 0, 0,0);
  paint.setColor(color);
  canvas.drawRoundRect(rectF,roundPX, roundPX, paint);
  paint.setXfermode(newPorterDuffXfermode(Mode.SRC_IN));
  canvas.drawBitmap(bitmap, rect,rect, paint);

  return dstbmp;
 }
}