[转载]Android缩放drawable

(2012-04-10 16:51:57) 转载▼

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分类：技术

原文地址：Android缩放drawable 作者：雨点点

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(Drawable drawable)// 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();
floatscale_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(Drawable drawable){

intwidth = 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 = new Canvas(bitmap);
drawable.setBounds(0, 0, width, height);

drawable.draw(canvas);

return bitmap;
}

public static Bitmap getRCB(Bitmap bitmap, float roundPX)//RCB means Rounded Corner Bitmap
{
Bitmap dstbmp = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), Config.ARGB_8888);
Canvas canvas = new Canvas(dstbmp);

final int color = 0xff424242;
final Paint paint = new Paint();
final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());
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 dstbmp;
}
}

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