Android(安卓)Bitmap常见用法

文章目录

@[toc]

1. 摄像头byte[]数据转为bitmap
2. bitmap转为byte[]数据
3. bitmap保存为图片
4. byte[]直接保存为图片
5. 从图片得到Bitmap
6. bitmap的裁剪
7. 从resource得到bitmap
参考链接

1. 摄像头byte[]数据转为bitmap

正确方法

public static Bitmap saveBGRA8888ByteToBitmap(byte[] data, int width, int height) {    byte[] bgraData = new byte[width*height*4];    System.arraycopy(data, 0, bgraData, 0, width*height*4);    Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);    ByteBuffer buf = ByteBuffer.wrap(bgraData);    bitmap.copyPixelsFromBuffer(buf);    return bitmap;}

这种方法在摄像头会出现getwidth NPE应该byte[]不包含这些数据

byte[] b = getIntent().getByteArrayExtra("bitmap");  Bitmap bitmap = BitmapFactory.decodeByteArray(b, 0, b.length);

2. bitmap转为byte[]数据

int bytes = bmp.getByteCount();ByteBuffer buf = ByteBuffer.allocate(bytes);bmp.copyPixelsToBuffer(buf);byte[] byteArray = buf.array();

3. bitmap保存为图片

/* * 保存bitmap到图片，PNG可以选择其他格式JPE PNG * @param bitmap原图 * @param savaPath保存文件的路径 */public static void saveBitmapToJpg(Bitmap bitmap, String savePath) {    File file=new File(savePath);    try {        FileOutputStream fos = new FileOutputStream(file);        bitmap.compress(Bitmap.CompressFormat.PNG, 100, fos);        fos.flush();        fos.close();    } catch (FileNotFoundException e) {        e.printStackTrace();    } catch (IOException e) {        e.printStackTrace();    }}    @frameworks/base/graphics/java/android/graphics/Bitmap.javapublic enum CompressFormat {    JPEG    (0),    PNG     (1),    WEBP    (2);        CompressFormat(int nativeInt) {        this.nativeInt = nativeInt;    }    final int nativeInt;}

4. byte[]直接保存为图片

/* *把BGRA格式的byte[]数据保存到图片 *@param data: 摄像头传过来的图像数据 *@param width: 图片的宽度 *@param height: 图片的高度 *@param savaPath保存文件的路径 */public static void saveBGRA8888ToPicture(byte[] data, int width, int height, String savePath) {    byte[] bgraData = new byte[width*height*4];    System.arraycopy(data, 0, bgraData, 0, width*height*4);    Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);    ByteBuffer buf = ByteBuffer.wrap(bgraData);    bitmap.copyPixelsFromBuffer(buf);    File file=new File(savePath);    if(file.exists()){        file.delete();    }    try {        FileOutputStream fos = new FileOutputStream(file);        bitmap.compress(Bitmap.CompressFormat.JPEG, 100, fos);        fos.flush();        fos.close();    } catch (FileNotFoundException e) {        e.printStackTrace();    } catch (IOException e) {        e.printStackTrace();    }    bitmap.recycle();}//适用于yuv格式的byte[]保存public static boolean saveYuvByteToJpegFile(byte[] bytes, int width, int height, String oldName){    FileOutputStream fileOutputStream = null;    ByteArrayOutputStream byteArrayOutputStream = null;    Bitmap bitmap = null;    String filePath = EXTERNAL_FILES_PATH + "/sensetime" + "/" + oldName + ".jpeg";    File fileDir = new File(EXTERNAL_FILES_PATH + "/sensetime");    if(!fileDir.exists() && !fileDir.mkdir()){        return false;    }    File file = new File(filePath);    try{        YuvImage yuvImage = new YuvImage(bytes, ImageFormat.NV21, width, height, null);        byteArrayOutputStream = new ByteArrayOutputStream();        yuvImage.compressToJpeg(new Rect(0, 0, width, height), 100, byteArrayOutputStream);        bitmap = BitmapFactory.decodeByteArray(byteArrayOutputStream.toByteArray(), 0, byteArrayOutputStream.size());        if(!file.exists() && !file.createNewFile()) return false;        fileOutputStream = new FileOutputStream(file);        return bitmap.compress(Bitmap.CompressFormat.JPEG, 100, fileOutputStream);    }catch (Exception e){        Log.e(TAG, e.toString());    }finally {        try{            if(fileOutputStream != null){                fileOutputStream.flush();                fileOutputStream.close();            }            if(byteArrayOutputStream != null){                byteArrayOutputStream.flush();                byteArrayOutputStream.close();            }            if(bitmap != null){                bitmap.recycle();                bitmap = null;            }        }catch (Exception e){            e.printStackTrace();        }    }    return false;}

5. 从图片得到Bitmap

会通过inSampleSize的值来压缩分辨率

public static Bitmap getImageResource(String imagePath){    Bitmap bitmap = null;    try{        BitmapFactory.Options options = new BitmapFactory.Options();        options.inJustDecodeBounds = true;        bitmap = BitmapFactory.decodeFile(imagePath, options);        int previewWidth = options.outWidth;        int previewHeight = options.outHeight;        options.inJustDecodeBounds = false;        if(previewWidth > 2560 || previewHeight > 2560) options.inSampleSize = 8;        else if(previewWidth > 1280 || previewHeight > 1280) options.inSampleSize = 4;        else if(previewWidth > 640 || previewHeight > 640) options.inSampleSize = 2;        options.inPreferredConfig = Bitmap.Config.ARGB_8888;        bitmap = BitmapFactory.decodeFile(imagePath, options);    }catch (Exception e){        e.printStackTrace();    }    return bitmap;}

6. bitmap的裁剪

//基本裁剪接口 public static Bitmap cropBitmap(Bitmap bitmap, int x, int y, int width, int height) {    return Bitmap.createBitmap(bitmap, x, y, width, height);}/* *@param bitmap: 原图 *@param x,y: 截取框第一个点的的xy坐标 *@param width: 截取bitmap的宽度 *@param height: 截取bitmap的高度 *@param newWidth newHeight 按上面参数截取后在压缩到newWidth newHeight尺寸 */public static Bitmap cropBitmap(Bitmap bitmap, int x, int y, int width, int height, int newWidth , int newHeight) {    Matrix matrix = new Matrix();    float scaleWidth = ((float) newWidth) / width;    float scaleHeight = ((float) newHeight) / height;    Log.e(TAG, "cropBitmap scaleWidth: " + scaleWidth + "  scaleHeight: " + scaleHeight);    matrix.postScale(scaleWidth, scaleHeight);    return Bitmap.createBitmap(bitmap, x, y, width, height, matrix, true );}

7. 从resource得到bitmap

bgra.jpg是width*heihgt 1280×720图片，在车技上得到bitmap的高度上正确的，而在pixel手机上为：
bitmap width: 3360 height:1890被拉伸了，要注意这种情况

UseBitmap(this, imageView , R.drawable.bgra);// 1.从资源中获取Bitmappublic void UseBitmap(Context context, ImageView imageView, int drawableId) {    Bitmap bitmap = BitmapFactory.decodeResource(context.getResources(), drawableId);    Log.d(TAG, "bitmap width: " + bitmap.getWidth() + " height:" + bitmap.getHeight());    Bitmap mbitmap = Bitmap.createBitmap(bitmap, 0 , 0 ,700 ,700);    Bitmap mmbitmap = Bitmap.createBitmap(mbitmap, 0 , 0 ,300 ,300);    Bitmap mmmbitmap = Bitmap.createBitmap(mmbitmap, 0 , 0 ,200 ,100);    imageView.setImageBitmap(mmmbitmap);    bitmap.recycle();    //mbitmap.recycle();}

参考链接

1. 开源一个 Android 图片压缩框架

2. Android Bitmap 和 ByteArray的互相转换

3. Android Bitmap最全面详解