为图像缩放图像

Question

在我的android应用程序中，我有一个用ImageViews和textViews填充的列表。 imageViews是从SD卡动态加载的。我的问题是我有更高分辨率的图像，为了列表的目的，我需要它们像缩略图一样小得多。那么如何将图像缩放为像imageView？

Answer 1

我希望下面这段代码是给你

public static Bitmap resizeImage(Bitmap orignal, int new_width, 
     int new_height) { 
    // load the origial BitMap 
    int width = orignal.getWidth(); 
    int height = orignal.getHeight(); 

    float scaleWidth = ((float) new_width)/width; 
    float scaleHeight = ((float) new_height)/height; 
    Matrix matrix = new Matrix(); 
    matrix.postScale(scaleWidth, scaleHeight); 
    Bitmap resizedBitmap = Bitmap.createBitmap(orignal, 0, 0, width, 
      height, matrix, true); 
    return resizedBitmap; 
} 

Answer 2

这里有用的是规模代码

private Bitmap decodeFile(File f){ 
    try { 
     //decode image size 
     BitmapFactory.Options o = new BitmapFactory.Options(); 
     o.inJustDecodeBounds = true; 
     BitmapFactory.decodeStream(new FileInputStream(f),null,o); 

     int scale=1; 
     //Find the correct scale value. It should be the power of 2. 
     final int REQUIRED_SIZE=250; // here provide your max size required 
     int width_tmp=o.outWidth, height_tmp=o.outHeight; 
     while(true){ 
      if(width_tmp/2<REQUIRED_SIZE || height_tmp/2<REQUIRED_SIZE) 
       break; 
      width_tmp/=2; 
      height_tmp/=2; 
      scale*=2; 
     } 

     //decode with inSampleSize 
     BitmapFactory.Options o2 = new BitmapFactory.Options(); 
     o2.inSampleSize=scale; 
     Bitmap bmp = BitmapFactory.decodeStream(new FileInputStream(f), null, o2); 
     return bmp; 
    } catch (FileNotFoundException e) {} 
    return null; 
} 

Answer 3

此代码可以帮助扩展您的图像根据您的ImageView

private void scaleImage() 
{ 
    // Get the ImageView and its bitmap 
    ImageView view = (ImageView) findViewById(R.id.image_box); 
    Drawable drawing = view.getDrawable(); 
    if (drawing == null) { 
     return; // Checking for null & return, as suggested in comments 
    } 
    Bitmap bitmap = ((BitmapDrawable)drawing).getBitmap(); 

    // Get current dimensions AND the desired bounding box 
    int width = bitmap.getWidth(); 
    int height = bitmap.getHeight(); 
    int bounding = dpToPx(250); 
    Log.i("Test", "original width = " + Integer.toString(width)); 
    Log.i("Test", "original height = " + Integer.toString(height)); 
    Log.i("Test", "bounding = " + Integer.toString(bounding)); 

    // Determine how much to scale: the dimension requiring less scaling is 
    // closer to the its side. This way the image always stays inside your 
    // bounding box AND either x/y axis touches it. 
    float xScale = ((float) bounding)/width; 
    float yScale = ((float) bounding)/height; 
    float scale = (xScale <= yScale) ? xScale : yScale; 
    Log.i("Test", "xScale = " + Float.toString(xScale)); 
    Log.i("Test", "yScale = " + Float.toString(yScale)); 
    Log.i("Test", "scale = " + Float.toString(scale)); 

    // Create a matrix for the scaling and add the scaling data 
    Matrix matrix = new Matrix(); 
    matrix.postScale(scale, scale); 

    // Create a new bitmap and convert it to a format understood by the ImageView 
    Bitmap scaledBitmap = Bitmap.createBitmap(bitmap, 0, 0, width, height, matrix, true); 
    width = scaledBitmap.getWidth(); // re-use 
    height = scaledBitmap.getHeight(); // re-use 
    BitmapDrawable result = new BitmapDrawable(scaledBitmap); 
    Log.i("Test", "scaled width = " + Integer.toString(width)); 
    Log.i("Test", "scaled height = " + Integer.toString(height)); 

    // Apply the scaled bitmap 
    view.setImageDrawable(result); 

    // Now change ImageView's dimensions to match the scaled image 
    LinearLayout.LayoutParams params = (LinearLayout.LayoutParams) view.getLayoutParams(); 
    params.width = width; 
    params.height = height; 
    view.setLayoutParams(params); 

    Log.i("Test", "done"); 
} 

private int dpToPx(int dp) 
{ 
    float density = getApplicationContext().getResources().getDisplayMetrics().density; 
    return Math.round((float)dp * density); 
} 

xml代码为ImageView：

<ImageView a:id="@+id/image_box" 
    a:background="#ff0000" 
    a:src="@drawable/star" 
    a:layout_width="wrap_content" 
    a:layout_height="wrap_content" 
    a:layout_marginTop="20dp" 
    a:layout_gravity="center_horizontal"/> 

礼貌：http://www.anddev.org/resize_and_rotate_image_-_example-t621.html

Answer 4

您也可以从图像视图中使用SETMAX：

imageView.setMaxHeight(myMaxHeight); 
imageView.setMaxWidth(myMaxWidth); 
imageView.setAdjustViewBounds(true); 
imageView.setScaleType(ScaleType.FIT_CENTER); 

您还可以使用该

的XML属性，使用这种方法的问题是你设置的最大尺寸，所以一个较小的图像将不会填充图像视图