Android - 缩放并压缩位图

Question

我正在开发一款安卓应用，该应用具有相机捕获和照片上传功能。如果设备具有高分辨率照相机，拍摄的图像尺寸将非常大（1〜3MB或更多）。
由于应用程序需要将此图像上传到服务器，因此我需要在上传前压缩图像。例如，如果相机捕获1920x1080全分辨率照片，理想的输出是保持图像的16：9比例，将其压缩为640x360图像，以降低某些图像质量并使其以较小的字节数进行缩小。

这是我的代码（来自谷歌引用）：

/** 
* 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; 
} 

与上述代码的问题是：

1. 它不能保持率，代码迫使图像大小调整为为480x800。如果用户以另一个比例捕捉图像，压缩后图像看起来不太好。

2. 它运行不正常。无论原始文件大小如何，代码将始终将图像大小更改为7990272byte。如果原始图像尺寸是非常小的已经，它将使大（我的测试结果把我的墙，这是非常单色的图片）：

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

我在问是否有更好的方式来压缩照片，以便它可以顺利上传的建议？

Answer 1

1. 您需要决定宽度或高度的限制（不是两个，显然）。然后替换那些固定的图像尺寸的计算的，说：

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

   （添加检查和横向/纵向姿态计算的替代品，如需要）。

2. 由于@harism也评论：大尺寸您提到的是原始大小，即480x800位图，而不是文件大小，在你的情况下应该是JPEG。你如何保存该位图，BTW？您的代码似乎不包含保存部分。

   用于对帮助，请参见this question here，关键是这样的：

   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

首先我检查图像的大小，然后我根据大小压缩图像，并得到压缩的位图，然后发送一个位图服务器 对于低于funtion压缩位电话我们必须通过以下funtion图像路径

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用于获取图像

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; 
}