android 圖片上傳前壓縮

參考：https://github.com/guizhigang/LGImageCompressor

詳解:

• 1.獲取本地圖片F(xiàn)ile文件 獲取BitmapFactory.Options對(duì)象 計(jì)算原始圖片 目標(biāo)圖片寬高比 計(jì)算輸出的圖片寬高

• 2.根據(jù)寬高比計(jì)算options.inSampleSize值（縮放比例 If set to a value > 1, requests the decoder to subsample the original image, returning a smaller image to save memory.）得到bitmap位圖 根據(jù)位圖對(duì)象獲取新的輸出位圖對(duì)象 Bitmap.createScaledBitmap(Bitmap src, int dstWidth, int dstHeight, boolean filter)Creates a new bitmap, scaled from an existing bitmap, whenpossible.

• 3.獲取圖片方向調(diào)整、失量壓縮圖片保持在1024kb以下

    //進(jìn)行大小縮放來(lái)達(dá)到壓縮的目的
    BitmapFactory.Options options = new BitmapFactory.Options();
    options.inJustDecodeBounds = true;
    BitmapFactory.decodeFile(srcImagePath, options);
    //根據(jù)原始圖片的寬高比和期望的輸出圖片的寬高比計(jì)算最終輸出的圖片的寬和高
  
    float srcWidth = options.outWidth;
    float srcHeight = options.outHeight;
    float maxWidth = outWidth;
    float maxHeight = outHeight;
    float srcRatio = srcWidth / srcHeight; //原始圖片寬高比
    float outRatio = maxWidth / maxHeight; //目標(biāo)圖片寬高比
    float actualOutWidth = srcWidth;
    float actualOutHeight = srcHeight;
     if (srcWidth > maxWidth || srcHeight > maxHeight) {
        if(srcRatio>outRatio){ //原始寬高比大于目標(biāo)寬高比
            actualOutWidth = maxWidth;
            actualOutHeight = actualOutWidth / srcRatio;
        }else if(srcRatio<outRatio){ //原始寬高比小于目標(biāo)寬高比
            actualOutHeight = maxHeight;
            actualOutWidth = actualOutHeight * srcRatio;
        }
    }else{
        actualOutWidth = maxWidth;
        actualOutHeight = maxHeight;
    }
  
    options.inSampleSize = computSampleSize(options, actualOutWidth, actualOutHeight);
    options.inJustDecodeBounds = false;
    Bitmap scaledBitmap = null;
    try {
        scaledBitmap = BitmapFactory.decodeFile(srcImagePath, options);
    } catch (OutOfMemoryError e) {
        e.printStackTrace();
    }
    if (scaledBitmap == null) {
        return null;
    }
    
      //生成最終輸出的bitmap
    Bitmap actualOutBitmap = Bitmap.createScaledBitmap(scaledBitmap, (int) actualOutWidth, (int) actualOutHeight, true);
    
    //釋放原始位圖資源
    if(scaledBitmap!=actualOutBitmap){ //判斷目標(biāo)位圖是否和原始位圖指向棧目標(biāo)相同
        scaledBitmap.recycle();
        scaledBitmap = null;
    }
    
     //處理圖片旋轉(zhuǎn)問(wèn)題
    ExifInterface exif = null;
    try {
        exif = new ExifInterface(srcImagePath);
        int orientation = exif.getAttributeInt(
                ExifInterface.TAG_ORIENTATION, 0);
        Matrix matrix = new Matrix();
        if (orientation == ExifInterface.ORIENTATION_ROTATE_90) {
            matrix.postRotate(90);
        } else if (orientation == ExifInterface.ORIENTATION_ROTATE_180) {
            matrix.postRotate(180);
        } else if (orientation == ExifInterface.ORIENTATION_ROTATE_270) {
            matrix.postRotate(270);
        }
        actualOutBitmap = Bitmap.createBitmap(actualOutBitmap, 0, 0,
                actualOutBitmap.getWidth(), actualOutBitmap.getHeight(), matrix, true);
    } catch (IOException e) {
        e.printStackTrace();
        return null;
    }
  
     //進(jìn)行有損壓縮
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    int options_ = 100;
    actualOutBitmap.compress(Bitmap.CompressFormat.JPEG, options_, baos);//質(zhì)量壓縮方法，把壓縮后的數(shù)據(jù)存放到baos中 (100表示不壓縮，0表示壓縮到最小)
  
    int baosLength = baos.toByteArray().length;
  
    while (baosLength / 1024 > maxFileSize) {//循環(huán)判斷如果壓縮后圖片是否大于maxMemmorrySize,大于繼續(xù)壓縮
        baos.reset();//重置baos即讓下一次的寫入覆蓋之前的內(nèi)容
        options_ = Math.max(0, options_ - 10);//圖片質(zhì)量每次減少10
        actualOutBitmap.compress(Bitmap.CompressFormat.JPEG, options_, baos);//將壓縮后的圖片保存到baos中
        baosLength = baos.toByteArray().length;
        if (options_ == 0)//如果圖片的質(zhì)量已降到最低則，不再進(jìn)行壓縮
            break;
    }
    actualOutBitmap.recycle();
  
    //將bitmap保存到指定路徑
    FileOutputStream fos = null;
    String filePath = getOutputFileName(srcImagePath);
    try {
        fos = new FileOutputStream(filePath);
        //包裝緩沖流,提高寫入速度
        BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(fos);
        bufferedOutputStream.write(baos.toByteArray());
        bufferedOutputStream.flush();
    } catch (FileNotFoundException e) {
        return null;
    } catch (IOException e) {
        return null;
    } finally {
        if (baos != null) {
            try {
                baos.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        if (fos != null) {
            try {
                fos.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
  
    //獲取位圖縮放比例
    private int computSampleSize(BitmapFactory.Options options, float reqWidth, float reqHeight) {
        float srcWidth = options.outWidth;//20
        float srcHeight = options.outHeight;//10
        int sampleSize = 1;
        if (srcWidth > reqWidth || srcHeight > reqHeight) {
            int withRatio = Math.round(srcWidth / reqWidth);
            int heightRatio = Math.round(srcHeight / reqHeight);
            sampleSize = Math.min(withRatio, heightRatio);
        }
        return sampleSize;
    }
  

壓縮比例換算：

float srcWidth = options.outWidth;
float srcHeight = options.outHeight;
float widthScale = outWidth / srcWidth;//目標(biāo)/原始 寬比例
float heightScale = outHeight / srcHeight; //目標(biāo)原始 高比
//對(duì)比寬高比選擇較大的一種比例
float scale = widthScale > heightScale ? widthScale : heightScale;
float actualOutWidth = srcWidth;
float actualOutHeight = srcHeight;
if (scale < 1) {
    actualOutWidth = srcWidth * scale;
    actualOutHeight = srcHeight * scale;
}

設(shè)置縮放比例--生成新的位圖

    Matrix matrix1 = new Matrix();
    matrix1.postScale(scale, scale);// 放大縮小比例
    //生成最終輸出的bitmap
    Bitmap actualOutBitmap = Bitmap.createBitmap(scaledBitmap, 0, 0, scaledBitmap.getWidth(), scaledBitmap.getHeight(), matrix1, true);

    if (actualOutBitmap != scaledBitmap) {
        scaledBitmap.recycle();
        scaledBitmap = null;
        System.gc();
    }