Android中图片Bitmap的缩放

一、什么是Android中的Bitmap

Bitmap是Android系统中的图像处理的最重要类之一。用它可以获取图像文件信息，进行图像剪切、旋转、缩放等操作，并可以指定格式保存图像文件。

二、Bitmap的缩放基本操作

在Android开发中，经常会遇到图片的操作问题，由于Android屏幕尺寸繁多，最经常的是图片的缩放问题。下面为一段Android操作的基本代码

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// 获得图片的宽高

int width = bm.getWidth();

int height = bm.getHeight();

// 设置想要的大小

int newWidth = 320;

int newHeight = 480;

// 计算缩放比例

float scaleWidth = ((float) newWidth) / width;

float scaleHeight = ((float) newHeight) / height;

// 取得想要缩放的matrix参数

Matrix matrix = new Matrix();

matrix.postScale(scaleWidth, scaleHeight);

// 得到新的图片

Bitmap newbm = Bitmap.createBitmap(bm, 0, 0, width, height, matrix,

true);

三、Bitmap缩放方法的封装

为了使用方便，我们对bitmap方法进行封装

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import java.io.ByteArrayInputStream;

import java.io.ByteArrayOutputStream;

import java.io.IOException;

import java.io.InputStream;

import android.content.Context;

import android.content.Intent;

import android.graphics.Bitmap;

import android.graphics.Bitmap.Config;

import android.graphics.BitmapFactory;

import android.graphics.Canvas;

import android.graphics.Matrix;

import android.net.Uri;

import android.util.Log;

public class Bitmaptest

{

private static final String TAG = "BitmapUtil";

/**

* 通过资源id转化成Bitmap

*

* @param context

* @param resId

* @return

*/

public static Bitmap ReadBitmapById(Context context, int resId)

{

BitmapFactory.Options opt = new BitmapFactory.Options();

opt.inPreferredConfig = Bitmap.Config.RGB_565;

opt.inPurgeable = true;

opt.inInputShareable = true;

InputStream is = context.getResources().openRawResource(resId);

return BitmapFactory.decodeStream(is, null, opt);

}

/**

* 缩放Bitmap满屏

*

* @param bitmap

* @param screenWidth

* @param screenHight

* @return

*/

public static Bitmap getBitmap(Bitmap bitmap, int screenWidth,

int screenHight)

{

int w = bitmap.getWidth();

int h = bitmap.getHeight();

Matrix matrix = new Matrix();

float scale = (float) screenWidth / w;

float scale2 = (float) screenHight / h;

// scale = scale < scale2 ? scale : scale2;

matrix.postScale(scale, scale);

Bitmap bmp = Bitmap.createBitmap(bitmap, 0, 0, w, h, matrix, true);

if (bitmap != null && !bitmap.equals(bmp) && !bitmap.isRecycled())

{

bitmap.recycle();

bitmap = null;

}

return bmp;// Bitmap.createBitmap(bitmap, 0, 0, w, h, matrix, true);

}

/**

* 按最大边按一定大小缩放图片

* */

public static Bitmap scaleImage(byte[] buffer, float size)

{

// 获取原图宽度

BitmapFactory.Options options = new BitmapFactory.Options();

options.inJustDecodeBounds = true;

options.inPurgeable = true;

options.inInputShareable = true;

Bitmap bm = BitmapFactory.decodeByteArray(buffer, 0, buffer.length,

options);

// 计算缩放比例

float reSize = options.outWidth / size;

if (options.outWidth < options.outHeight)

{

reSize = options.outHeight / size;

}

// 如果是小图则放大

if (reSize <= 1)

{

int newWidth = 0;

int newHeight = 0;

if (options.outWidth > options.outHeight)

{

newWidth = (int) size;

newHeight = options.outHeight * (int) size / options.outWidth;

} else

{

newHeight = (int) size;

newWidth = options.outWidth * (int) size / options.outHeight;

}

bm = BitmapFactory.decodeByteArray(buffer, 0, buffer.length);

bm = scaleImage(bm, newWidth, newHeight);

if (bm == null)

{

Log.e(TAG, "convertToThumb, decode fail:" + null);

return null;

}

return bm;

}

// 缩放

options.inJustDecodeBounds = false;

options.inSampleSize = (int) reSize;

bm = BitmapFactory.decodeByteArray(buffer, 0, buffer.length, options);

if (bm == null)

{

Log.e(TAG, "convertToThumb, decode fail:" + null);

return null;

}

return bm;

}

/**

* 检查图片是否超过一定值，是则缩小

*

* @param view

* @param strFileName

*/

public static Bitmap convertToThumb(byte[] buffer, float size)

{

// 获取原图宽度

BitmapFactory.Options options = new BitmapFactory.Options();

options.inJustDecodeBounds = true;

options.inPurgeable = true;

options.inInputShareable = true;

Bitmap bm = BitmapFactory.decodeByteArray(buffer, 0, buffer.length,

options);

// 计算缩放比例

float reSize = options.outWidth / size;

if (options.outWidth > options.outHeight)

{

reSize = options.outHeight / size;

}

if (reSize <= 0)

{

reSize = 1;

}

Log.d(TAG, "convertToThumb, reSize:" + reSize);

// 缩放

options.inJustDecodeBounds = false;

options.inSampleSize = (int) reSize;

if (bm != null && !bm.isRecycled())

{

bm.recycle();

bm = null;

Log.e(TAG, "convertToThumb, recyle");

}

bm = BitmapFactory.decodeByteArray(buffer, 0, buffer.length, options);

if (bm == null)

{

Log.e(TAG, "convertToThumb, decode fail:" + null);

return null;

}

return bm;

}

/**

* Bitmap --> byte[]

*

* @param bmp

* @return

*/

private static byte[] readBitmap(Bitmap bmp)

{

ByteArrayOutputStream baos = new ByteArrayOutputStream();

bmp.compress(Bitmap.CompressFormat.JPEG, 60, baos);

try

{

baos.flush();

baos.close();

} catch (IOException e)

{

e.printStackTrace();

}

return baos.toByteArray();

}

/**

* Bitmap --> byte[]

*

* @param bmp

* @return

*/

public static byte[] readBitmapFromBuffer(byte[] buffer, float size)

{

return readBitmap(convertToThumb(buffer, size));

}

/**

* 以屏幕宽度为基准，显示图片

*

* @param iv

* @param path

* @param screenW

* @return

*/

public static Bitmap decodeStream(Context context, Intent data, float size)

{

Bitmap image = null;

try

{

Uri dataUri = data.getData();

// 获取原图宽度

BitmapFactory.Options options = new BitmapFactory.Options();

options.inJustDecodeBounds = true;

options.inPurgeable = true;

options.inInputShareable = true;

BitmapFactory.decodeStream(context.getContentResolver()

.openInputStream(dataUri), null, options);

// 计算缩放比例

float reSize = (int) (options.outWidth / size);

if (reSize <= 0)

{

reSize = 1;

}

Log.d(TAG, "old-w:" + options.outWidth + ", llyt-w:" + size

+ ", resize:" + reSize);

// 缩放

options.inJustDecodeBounds = false;

options.inSampleSize = (int) reSize;

image = BitmapFactory.decodeStream(context.getContentResolver()

.openInputStream(dataUri), null, options);

} catch (Exception e)

{

e.printStackTrace();

}

return image;

}

/**

* 按新的宽高缩放图片

*

* @param bm

* @param&n
2b528
bsp;newWidth

* @param newHeight

* @return

*/

public static Bitmap scaleImage(Bitmap bm, int newWidth, int newHeight)

{

if (bm == null)

{

return null;

}

int width = bm.getWidth();

int height = bm.getHeight();

float scaleWidth = ((float) newWidth) / width;

float scaleHeight = ((float) newHeight) / height;

Matrix matrix = new Matrix();

matrix.postScale(scaleWidth, scaleHeight);

Bitmap newbm = Bitmap.createBitmap(bm, 0, 0, width, height, matrix,

true);

if (bm != null & !bm.isRecycled())

{

bm.recycle();

bm = null;

}

return newbm;

}

/**

* fuction: 设置固定的宽度，高度随之变化，使图片不会变形

*

* @param target

* 需要转化bitmap参数

* @param newWidth

* 设置新的宽度

* @return

*/

public static Bitmap fitBitmap(Bitmap target, int newWidth)

{

int width = target.getWidth();

int height = target.getHeight();

Matrix matrix = new Matrix();

float scaleWidth = ((float) newWidth) / width;

// float scaleHeight = ((float)newHeight) / height;

int newHeight = (int) (scaleWidth * height);

matrix.postScale(scaleWidth, scaleWidth);

// Bitmap result = Bitmap.createBitmap(target,0,0,width,height,

// matrix,true);

Bitmap bmp = Bitmap.createBitmap(target, 0, 0, width, height, matrix,

true);

if (target != null && !target.equals(bmp) && !target.isRecycled())

{

target.recycle();

target = null;

}

return bmp;// Bitmap.createBitmap(target, 0, 0, width, height, matrix,

// true);

}

/**

* 根据指定的宽度平铺图像

*

* @param width

* @param src

* @return

*/

public static Bitmap createRepeater(int width, Bitmap src)

{

int count = (width + src.getWidth() - 1) / src.getWidth();

Bitmap bitmap = Bitmap.createBitmap(width, src.getHeight(),

Config.ARGB_8888);

Canvas canvas = new Canvas(bitmap);

for (int idx = 0; idx < count; ++idx)

{

canvas.drawBitmap(src, idx * src.getWidth(), 0, null);

}

return bitmap;

}

/**

* 图片的质量压缩方法

*

* @param image

* @return

*/

public static Bitmap compressImage(Bitmap image)

{

ByteArrayOutputStream baos = new ByteArrayOutputStream();

image.compress(Bitmap.CompressFormat.JPEG, 100, baos);// 质量压缩方法，这里100表示不压缩，把压缩后的数据存放到baos中

int options = 100;

while (baos.toByteArray().length / 1024 > 100)

{ // 循环判断如果压缩后图片是否大于100kb,大于继续压缩

baos.reset();// 重置baos即清空baos

image.compress(Bitmap.CompressFormat.JPEG, options, baos);// 这里压缩options%，把压缩后的数据存放到baos中

options -= 10;// 每次都减少10

}

ByteArrayInputStream isBm = new ByteArrayInputStream(baos.toByteArray());// 把压缩后的数据baos存放到ByteArrayInputStream中

Bitmap bitmap = BitmapFactory.decodeStream(isBm, null, null);// 把ByteArrayInputStream数据生成图片

if (baos != null)

{

try

{

baos.close();

} catch (IOException e)

{

// TODO Auto-generated catch block

e.printStackTrace();

}

}

if (isBm != null)

{

try

{

isBm.close();

} catch (IOException e)

{

// TODO Auto-generated catch block

e.printStackTrace();

}

}

if (image != null && !image.isRecycled())

{

image.recycle();

image = null;

}

return bitmap;

}

/**

* 图片按比例大小压缩方法(根据Bitmap图片压缩)

*

* @param image

* @return

*/

public static Bitmap getImage(Bitmap image)

{

ByteArrayOutputStream baos = new ByteArrayOutputStream();

image.compress(Bitmap.CompressFormat.JPEG, 100, baos);

if (baos.toByteArray().length / 1024 > 1024)

{// 判断如果图片大于1M,进行压缩避免在生成图片（BitmapFactory.decodeStream）时溢出

baos.reset();// 重置baos即清空baos

image.compress(Bitmap.CompressFormat.JPEG, 50, baos);// 这里压缩50%，把压缩后的数据存放到baos中

}

ByteArrayInputStream isBm = new ByteArrayInputStream(baos.toByteArray());

BitmapFactory.Options newOpts = new BitmapFactory.Options();

// 开始读入图片，此时把options.inJustDecodeBounds 设回true了

newOpts.inJustDecodeBounds = true;

Bitmap bitmap = BitmapFactory.decodeStream(isBm, null, newOpts);

newOpts.inJustDecodeBounds = false;

int w = newOpts.outWidth;

int h = newOpts.outHeight;

// 现在主流手机比较多是800*480分辨率，所以高和宽我们设置为

float hh = 800f;// 这里设置高度为800f

float ww = 480f;// 这里设置宽度为480f

// 缩放比。由于是固定比例缩放，只用高或者宽其中一个数据进行计算即可

int be = 1;// be=1表示不缩放

if (w > h && w > ww)

{// 如果宽度大的话根据宽度固定大小缩放

be = (int) (newOpts.outWidth / ww);

} else if (w < h && h > hh)

{// 如果高度高的话根据宽度固定大小缩放

be = (int) (newOpts.outHeight / hh);

}

if (be <= 0)

be = 1;

newOpts.inSampleSize = be;// 设置缩放比例

// 重新读入图片，注意此时已经把options.inJustDecodeBounds 设回false了

isBm = new ByteArrayInputStream(baos.toByteArray());

bitmap = BitmapFactory.decodeStream(isBm, null, newOpts);

if (isBm != null)

{

try

{

isBm.close();

} catch (IOException e)

{

// TODO Auto-generated catch block

e.printStackTrace();

}

}

if (image != null && !image.isRecycled())

{

image.recycle();

image = null;

}

return compressImage(bitmap);// 压缩好比例大小后再进行质量压缩

}

/**

* 通过资源id转化成Bitmap 全屏显示

*

* @param context

* @param drawableId

* @param screenWidth

* @param screenHight

* @return

*/

public static Bitmap ReadBitmapById(Context context, int drawableId,

int screenWidth, int screenHight)

{

BitmapFactory.Options options = new BitmapFactory.Options();

options.inPreferredConfig = Config.ARGB_8888;

options.inInputShareable = true;

options.inPurgeable = true;

InputStream stream = context.getResources().openRawResource(drawableId);

Bitmap bitmap = BitmapFactory.decodeStream(stream, null, options);

return getBitmap(bitmap, screenWidth, screenHight);

}

}

示例代码：http://download.csdn.net/detail/stop_pig/7162695

转载地址：http://blog.csdn.net/stoppig/article/details/23198809