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;

}

}