.9的左上右下黑线，是什么？外加google的下载图片并缓存本地的方法-优快云博客

本文介绍了一种图片缩放和压缩的方法，包括如何获取图片原始尺寸、确定目标宽度及计算缩放比例，并通过BitmapFactory进行图片解码，最终保存为指定格式。此方法有助于减少内存使用并保持图片质量。

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Notice the black pixels along the borders. The ones on the top and left borders indicate the places where the image can be stretched, and the ones on the right and bottom borders indicate where the content should be placed.


  // Get the source image's dimensions
  BitmapFactory.Options options = new BitmapFactory.Options();
  // This does not download the actual image, just downloads headers.
  options.inJustDecodeBounds = true; 
  BitmapFactory.decodeFile(IMAGE_FILE_URL, options);
  // The actual width of the image.
  int srcWidth = options.outWidth;  
  // The actual height of the image.
  int srcHeight = options.outHeight;  

  // Only scale if the source is bigger than the width of the destination view.
  if(desiredWidth > srcWidth)
    desiredWidth = srcWidth;

  // Calculate the correct inSampleSize/scale value. This helps reduce memory use. It should be a power of 2.
  int inSampleSize = 1;
  while(srcWidth / 2 > desiredWidth){
    srcWidth /= 2;
    srcHeight /= 2;
    inSampleSize *= 2;
  }

  float desiredScale = (float) desiredWidth / srcWidth;

  // Decode with inSampleSize
  options.inJustDecodeBounds = false;
  options.inDither = false;
  options.inSampleSize = inSampleSize;
  options.inScaled = false;
  // Ensures the image stays as a 32-bit ARGB_8888 image.
  // This preserves image quality.
  options.inPreferredConfig = Bitmap.Config.ARGB_8888;  

  Bitmap sampledSrcBitmap = BitmapFactory.decodeFile(IMAGE_FILE_URL, options);

  // Resize
  Matrix matrix = new Matrix();
  matrix.postScale(desiredScale, desiredScale);
  Bitmap scaledBitmap = Bitmap.createBitmap(sampledSrcBitmap, 0, 0,
      sampledSrcBitmap.getWidth(), sampledSrcBitmap.getHeight(), matrix, true);
  sampledSrcBitmap = null;

  // Save
  FileOutputStream out = new FileOutputStream(LOCAL_PATH_TO_STORE_IMAGE);
  scaledBitmap.compress(Bitmap.CompressFormat.JPEG, 100, out);
  scaledBitmap = null;