Android Bitmap詳細介紹

從別人的文章裏面摳過來的，還沒來的及整理，先放着，有空的時候再整理，以爲有用的朋友能夠參考一下。

Android中Bitmap的常見操做一覽，代碼以下：

package com.testbitmapscale; 
import java.io.File; 
import java.io.FileInputStream; 
import java.io.FileOutputStream; 
import java.io.IOException; 
import java.io.InputStream; 
import java.util.Iterator; 
import com.testbitmapscale.R.drawable; 
import android.app.Activity; 
import android.graphics.Bitmap; 
import android.graphics.Bitmap.Config; 
import android.graphics.BitmapFactory; 
import android.graphics.Canvas; 
import android.graphics.Matrix; 
import android.graphics.Paint; 
import android.graphics.PorterDuff.Mode; 
import android.graphics.PorterDuffXfermode; 
import android.graphics.Rect; 
import android.graphics.RectF; 
import android.graphics.drawable.BitmapDrawable; 
import android.graphics.drawable.Drawable; 
import android.media.ThumbnailUtils; 
import android.os.Bundle; 
import android.os.Environment; 
import android.view.View; 
import android.widget.ImageView; 
//方法: 
//1 生成圓角Bitmap圖片 
//2 生成Bitmap縮量圖 
//3 壓縮圖片場長寬以及kB 
//注意: 
//以上代碼,測試其中一個方法時最好註釋掉其他的代碼 
public class MainActivity extends Activity { 
private ImageView imageView; 
private Bitmap copyRawBitmap1; 
private Bitmap copyRawBitmap2; 
private Bitmap copyRawBitmap3; 
@Override 
public void onCreate(Bundle savedInstanceState) { 
super.onCreate(savedInstanceState); 
setContentView(R.layout.main); 
imageView = (ImageView) findViewById(R.id.imageView); 
//第一種方式:從資源文件中獲得圖片 
Bitmap rawBitmap = BitmapFactory.decodeResource(getResources(),R.drawable.haha); 
copyRawBitmap1=rawBitmap; 
copyRawBitmap2=rawBitmap; 
copyRawBitmap3=rawBitmap; 
//第二種方式:從SD卡中獲得圖片(方法1) 
String SDCarePath=Environment.getExternalStorageDirectory().toString(); 
String filePath=SDCarePath+"/"+"haha.jpg"; 
Bitmap rawBitmap1 = BitmapFactory.decodeFile(filePath, null); 
//第二種方式:從SD卡中獲得圖片(方法2) 
InputStream inputStream=getBitmapInputStreamFromSDCard("haha.jpg"); 
Bitmap rawBitmap2 = BitmapFactory.decodeStream(inputStream); 

//————>如下爲將設置圖片的圓角 
Bitmap roundCornerBitmap=this.toRoundCorner(rawBitmap, 40); 
imageView.setImageBitmap(roundCornerBitmap); 
//————>以上爲將設置圖片的圓角 

//————>如下爲將圖片高寬和的大小kB壓縮 
// 獲得圖片原始的高寬 
int rawHeight = rawBitmap.getHeight(); 
int rawWidth = rawBitmap.getWidth(); 
// 設定圖片新的高寬 
int newHeight = 500; 
int newWidth = 500; 
// 計算縮放因子 
float heightScale = ((float) newHeight) / rawHeight; 
float widthScale = ((float) newWidth) / rawWidth; 
// 新創建矩陣 
Matrix matrix = new Matrix(); 
matrix.postScale(heightScale, widthScale); 
// 設置圖片的旋轉角度 
//matrix.postRotate(-30); 
// 設置圖片的傾斜 
//matrix.postSkew(0.1f, 0.1f); 
//將圖片大小壓縮 
//壓縮後圖片的寬和高以及kB大小均會變化 
Bitmap newBitmap = Bitmap.createBitmap(rawBitmap, 0, 0, rawWidth,rawWidth, matrix, true); 
// 將Bitmap轉換爲Drawable 
Drawable newBitmapDrawable = new BitmapDrawable(newBitmap); 
imageView.setImageDrawable(newBitmapDrawable); 
//而後將Bitmap保存到SDCard中,方便於原圖片的比較 
this.compressAndSaveBitmapToSDCard(newBitmap, "xx100.jpg", 80); 
//問題: 
//原圖大小爲625x690 90.2kB 
//若是設置圖片500x500 壓縮後大小爲171kB.即壓縮後kB反而變大了. 
//緣由是將:compress(Bitmap.CompressFormat.JPEG, quality, fileOutputStream); 
//第二個參數quality設置得有些大了(好比100). 
//經常使用的是80,剛設100太大了形成的. 
//————>以上爲將圖片高寬和的大小kB壓縮 


//————>如下爲將圖片的kB壓縮,寬高不變 
this.compressAndSaveBitmapToSDCard(copyRawBitmap1,"0011fa.jpg",80); 
//————>以上爲將圖片的kB壓縮,寬高不變 

//————>如下爲獲取SD卡圖片的縮略圖方法1 
String SDCarePath1=Environment.getExternalStorageDirectory().toString(); 
String filePath1=SDCarePath1+"/"+"haha.jpg"; 
Bitmap bitmapThumbnail1=this.getBitmapThumbnail(filePath1); 
imageView.setImageBitmap(bitmapThumbnail1); 
//————>以上爲獲取SD卡圖片的縮略圖方法1 

//————>如下爲獲取SD卡圖片的縮略圖方法2 
String SDCarePath2=Environment.getExternalStorageDirectory().toString(); 
String filePath2=SDCarePath2+"/"+"haha.jpg"; 
Bitmap tempBitmap=BitmapFactory.decodeFile(filePath2); 
Bitmap bitmapThumbnail2=ThumbnailUtils.extractThumbnail(tempBitmap, 100, 100); 
imageView.setImageBitmap(bitmapThumbnail2); 
//————>以上爲獲取SD卡圖片的縮略圖方法2 

} 
//讀取SD卡下的圖片 
private InputStream getBitmapInputStreamFromSDCard(String fileName){ 
if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) { 
String SDCarePath=Environment.getExternalStorageDirectory().toString(); 
String filePath=SDCarePath+File.separator+fileName; 
File file=new File(filePath); 
try { 
FileInputStream fileInputStream=new FileInputStream(file); 
return fileInputStream; 
} catch (Exception e) { 
e.printStackTrace(); 
} 

} 
return null; 
} 


//獲取SDCard的目錄路徑功能 
private String getSDCardPath() { 
String SDCardPath = null; 
// 判斷SDCard是否存在 
boolean IsSDcardExist = Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED); 
if (IsSDcardExist) { 
SDCardPath = Environment.getExternalStorageDirectory().toString(); 
} 
return SDCardPath; 
} 
//壓縮且保存圖片到SDCard 
private void compressAndSaveBitmapToSDCard(Bitmap rawBitmap,String fileName,int quality){ 
String saveFilePaht=this.getSDCardPath()+File.separator+fileName; 
File saveFile=new File(saveFilePaht); 
if (!saveFile.exists()) { 
try { 
saveFile.createNewFile(); 
FileOutputStream fileOutputStream=new FileOutputStream(saveFile); 
if (fileOutputStream!=null) { 
//imageBitmap.compress(format, quality, stream); 
//把位圖的壓縮信息寫入到一個指定的輸出流中 
//第一個參數format爲壓縮的格式 
//第二個參數quality爲圖像壓縮比的值,0-100.0 意味着小尺寸壓縮,100意味着高質量壓縮 
//第三個參數stream爲輸出流 
rawBitmap.compress(Bitmap.CompressFormat.JPEG, quality, fileOutputStream); 
} 
fileOutputStream.flush(); 
fileOutputStream.close(); 
} catch (IOException e) { 
e.printStackTrace(); 

} 
} 
} 

//獲取圖片的縮略圖 
private Bitmap getBitmapThumbnail(String filePath){ 
BitmapFactory.Options options=new BitmapFactory.Options(); 
//true那麼將不返回實際的bitmap對象,不給其分配內存空間可是能夠獲得一些解碼邊界信息即圖片大小等信息 
options.inJustDecodeBounds=true; 
//此時rawBitmap爲null 
Bitmap rawBitmap = BitmapFactory.decodeFile(filePath, options); 
if (rawBitmap==null) { 
System.out.println("此時rawBitmap爲null"); 
} 
//inSampleSize表示縮略圖大小爲原始圖片大小的幾分之一,若該值爲3 
//則取出的縮略圖的寬和高都是原始圖片的1/3,圖片大小就爲原始大小的1/9 
//計算sampleSize 
int sampleSize=computeSampleSize(options, 150, 200*200); 
//爲了讀到圖片,必須把options.inJustDecodeBounds設回false 
options.inJustDecodeBounds = false; 
options.inSampleSize = sampleSize; 
//原圖大小爲625x690 90.2kB 
//測試調用computeSampleSize(options, 100, 200*100); 
//獲得sampleSize=8 
//獲得寬和高位79和87 
//79*8=632 87*8=696 
Bitmap thumbnailBitmap=BitmapFactory.decodeFile(filePath, options); 
//保存到SD卡方便比較 
this.compressAndSaveBitmapToSDCard(thumbnailBitmap, "15.jpg", 80); 
return thumbnailBitmap; 
} 

//參考資料： 
//http://my.csdn.net/zljk000/code/detail/18212 
//第一個參數:本來Bitmap的options 
//第二個參數:但願生成的縮略圖的寬高中的較小的值 
//第三個參數:但願生成的縮量圖的總像素 
public static int computeSampleSize(BitmapFactory.Options options,int minSideLength, int maxNumOfPixels) { 
int initialSize = computeInitialSampleSize(options, minSideLength,maxNumOfPixels); 
int roundedSize; 
if (initialSize <= 8) { 
roundedSize = 1; 
while (roundedSize < initialSize) { 
roundedSize <<= 1; 
} 
} else { 
roundedSize = (initialSize + 7) / 8 * 8; 
} 
return roundedSize; 
} 

private static int computeInitialSampleSize(BitmapFactory.Options options,int minSideLength, int maxNumOfPixels) { 
//原始圖片的寬 
double w = options.outWidth; 
//原始圖片的高 
double h = options.outHeight; 
System.out.println("========== w="+w+",h="+h); 
int lowerBound = (maxNumOfPixels == -1) ? 1 : (int) Math.ceil(Math 
.sqrt(w * h / maxNumOfPixels)); 
int upperBound = (minSideLength == -1) ? 128 : (int) Math.min( 
Math.floor(w / minSideLength), Math.floor(h / minSideLength)); 
if (upperBound < lowerBound) { 
// return the larger one when there is no overlapping zone. 
return lowerBound; 
} 
if ((maxNumOfPixels == -1) && (minSideLength == -1)) { 
return 1; 
} else if (minSideLength == -1) { 
return lowerBound; 
} else { 
return upperBound; 
} 
} 

/** 
* @param bitmap 須要修改的圖片 
* @param pixels 圓角的弧度 
* @return 圓角圖片 
*/ 
//參考資料: 
//http://blog.csdn.net/c8822882/article/details/6906768 
public Bitmap toRoundCorner(Bitmap bitmap, int pixels) { 
Bitmap roundCornerBitmap = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), Config.ARGB_8888); 
Canvas canvas = new Canvas(roundCornerBitmap); 
int color = 0xff424242;//int color = 0xff424242; 
Paint paint = new Paint(); 
paint.setColor(color); 
//防止鋸齒 
paint.setAntiAlias(true); 
Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight()); 
RectF rectF = new RectF(rect); 
float roundPx = pixels; 
//至關於清屏 
canvas.drawARGB(0, 0, 0, 0); 
//先畫了一個帶圓角的矩形 
canvas.drawRoundRect(rectF, roundPx, roundPx, paint); 
paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN)); 
//再把原來的bitmap畫到如今的bitmap！！！注意這個理解 
canvas.drawBitmap(bitmap, rect, rect, paint); 
return roundCornerBitmap; 
} 

}