Android - 縮放並壓縮位圖

Question

我正在開發一款安卓應用，該應用具有相機捕獲和照片上傳功能。如果設備具有高分辨率照相機，拍攝的圖像尺寸將非常大（1〜3MB或更多）。
由於應用程序需要將此圖像上傳到服務器，因此我需要在上傳前壓縮圖像。例如，如果相機捕獲1920x1080全分辨率照片，理想的輸出是保持圖像的16：9比例，將其壓縮爲640x360圖像，以降低某些圖像質量並使其以較小的字節數進行縮小。

這是我的代碼（來自谷歌引用）：

/** 
* this class provide methods that can help compress the image size. 
* 
*/ 
public class ImageCompressHelper { 

/** 
* Calcuate how much to compress the image 
* @param options 
* @param reqWidth 
* @param reqHeight 
* @return 
*/ 
public static int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) { 
// Raw height and width of image 
final int height = options.outHeight; 
final int width = options.outWidth; 
int inSampleSize = 1; 

if (height > reqHeight || width > reqWidth) { 

    final int halfHeight = height/2; 
    final int halfWidth = width/2; 

    // Calculate the largest inSampleSize value that is a power of 2 and keeps both 
    // height and width larger than the requested height and width. 
    while ((halfHeight/inSampleSize) > reqHeight 
      && (halfWidth/inSampleSize) > reqWidth) { 
     inSampleSize *= 2; 
    } 
} 

return inSampleSize; 
} 

/** 
* resize image to 480x800 
* @param filePath 
* @return 
*/ 
public static Bitmap getSmallBitmap(String filePath) { 

    File file = new File(filePath); 
    long originalSize = file.length(); 

    MyLogger.Verbose("Original image size is: " + originalSize + " bytes."); 

    final BitmapFactory.Options options = new BitmapFactory.Options(); 
    options.inJustDecodeBounds = true; 
    BitmapFactory.decodeFile(filePath, options); 

    // Calculate inSampleSize based on a preset ratio 
    options.inSampleSize = calculateInSampleSize(options, 480, 800); 

    // Decode bitmap with inSampleSize set 
    options.inJustDecodeBounds = false; 

    Bitmap compressedImage = BitmapFactory.decodeFile(filePath, options); 

    MyLogger.Verbose("Compressed image size is " + sizeOf(compressedImage) + " bytes"); 

    return compressedImage; 
} 

與上述代碼的問題是：

1. 它不能保持率，代碼迫使圖像大小調整爲爲480x800。如果用戶以另一個比例捕捉圖像，壓縮後圖像看起來不太好。

2. 它運行不正常。無論原始文件大小如何，代碼將始終將圖像大小更改爲7990272byte。如果原始圖像尺寸是非常小的已經，它將使大（我的測試結果把我的牆，這是非常單色的圖片）：

   Original image size is: 990092 bytes.
Compressed image size is 7990272 bytes

我在問是否有更好的方式來壓縮照片，以便它可以順利上傳的建議？

Answer 1

1. 您需要決定寬度或高度的限制（不是兩個，顯然）。然後替換那些固定的圖像尺寸的計算的，說：

   int targetWidth = 640; // your arbitrary fixed limit 
   int targetHeight = (int) (originalHeight * targetWidth/(double) originalWidth); // casts to avoid truncating 
   

   （添加檢查和橫向/縱向姿態計算的替代品，如需要）。

2. 由於@harism也評論：大尺寸您提到的是原始大小，即480x800位圖，而不是文件大小，在你的情況下應該是JPEG。你如何保存該位圖，BTW？您的代碼似乎不包含保存部分。

   用於對幫助，請參見this question here，關鍵是這樣的：

   OutputStream imagefile = new FileOutputStream("/your/file/name.jpg"); 
   // Write 'bitmap' to file using JPEG and 80% quality hint for JPEG: 
   bitmap.compress(CompressFormat.JPEG, 80, imagefile); 
   

Answer 2

首先我檢查圖像的大小，然後我根據大小壓縮圖像，並得到壓縮的位圖，然後發送一個位圖服務器 對於低於funtion壓縮位電話我們必須通過以下funtion圖像路徑

public Bitmap get_Picture_bitmap(String imagePath) { 

    long size_file = getFileSize(new File(imagePath)); 

    size_file = (size_file)/1000;// in Kb now 
    int ample_size = 1; 

    if (size_file <= 250) { 

     System.out.println("SSSSS1111= " + size_file); 
     ample_size = 2; 

    } else if (size_file > 251 && size_file < 1500) { 

     System.out.println("SSSSS2222= " + size_file); 
     ample_size = 4; 

    } else if (size_file >= 1500 && size_file < 3000) { 

     System.out.println("SSSSS3333= " + size_file); 
     ample_size = 8; 

    } else if (size_file >= 3000 && size_file <= 4500) { 

     System.out.println("SSSSS4444= " + size_file); 
     ample_size = 12; 

    } else if (size_file >= 4500) { 

     System.out.println("SSSSS4444= " + size_file); 
     ample_size = 16; 
    } 

    Bitmap bitmap = null; 

    BitmapFactory.Options bitoption = new BitmapFactory.Options(); 
    bitoption.inSampleSize = ample_size; 

    Bitmap bitmapPhoto = BitmapFactory.decodeFile(imagePath, bitoption); 

    ExifInterface exif = null; 
    try { 
     exif = new ExifInterface(imagePath); 
    } catch (IOException e) { 
     // Auto-generated catch block 
     e.printStackTrace(); 
    } 
    int orientation = exif 
      .getAttributeInt(ExifInterface.TAG_ORIENTATION, 1); 
    Matrix matrix = new Matrix(); 

    if ((orientation == 3)) { 
     matrix.postRotate(180); 
     bitmap = Bitmap.createBitmap(bitmapPhoto, 0, 0, 
       bitmapPhoto.getWidth(), bitmapPhoto.getHeight(), matrix, 
       true); 

    } else if (orientation == 6) { 
     matrix.postRotate(90); 
     bitmap = Bitmap.createBitmap(bitmapPhoto, 0, 0, 
       bitmapPhoto.getWidth(), bitmapPhoto.getHeight(), matrix, 
       true); 

    } else if (orientation == 8) { 
     matrix.postRotate(270); 
     bitmap = Bitmap.createBitmap(bitmapPhoto, 0, 0, 
       bitmapPhoto.getWidth(), bitmapPhoto.getHeight(), matrix, 
       true); 

    } else { 
     matrix.postRotate(0); 
     bitmap = Bitmap.createBitmap(bitmapPhoto, 0, 0, 
       bitmapPhoto.getWidth(), bitmapPhoto.getHeight(), matrix, 
       true); 

    } 

    return bitmap; 

} 

getFileSize funtion用於獲取圖像

public long getFileSize(final File file) { 
    if (file == null || !file.exists()) 
     return 0; 
    if (!file.isDirectory()) 
     return file.length(); 
    final List<File> dirs = new LinkedList<File>(); 
    dirs.add(file); 
    long result = 0; 
    while (!dirs.isEmpty()) { 
     final File dir = dirs.remove(0); 
     if (!dir.exists()) 
      continue; 
     final File[] listFiles = dir.listFiles(); 
     if (listFiles == null || listFiles.length == 0) 
      continue; 
     for (final File child : listFiles) { 
      result += child.length(); 
      if (child.isDirectory()) 
       dirs.add(child); 
     } 
    } 

    return result; 
}