android 图片采样缩放 Android图片采样缩放功能实例代码

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.BitmapFactory.Options;
import android.util.DisplayMetrics;
import android.view.ViewGroup.LayoutParams;
import android.widget.ImageView;
public class ImagesTool 
{
  /**
   * 根据ImageView的大小压缩图片
   * @param path
   * @param imageView
   * @return
   */
  public static Bitmap decodeSampledBitmapFromPath(String path,ImageView imageView)
  {
    Options options = new Options();
    options.inJustDecodeBounds=true;
    BitmapFactory.decodeFile(path,options);
    ImageSize imageSize=getImageViewSize(imageView); //获取图片大小，ImageSize是封装着ImageView大小的类
    //计算采样率
    options.inSampleSize=caculateInSampleSize(options,imageSize.width,imageSize.height);
    options.inJustDecodeBounds=false;
    Bitmap bitmap=BitmapFactory.decodeFile(path, options);
    return bitmap;
  }
  //计算采样率
  public static int caculateInSampleSize(Options options,ImageView imageView)
  {
    ImageSize imageSize=getImageViewSize(imageView);
    int inSampleSize=caculateInSampleSize(options, imageSize.width,imageSize.height);
    return inSampleSize;
  }
  /**
   * 根据具体的大小要求解析图片
   * @param path
   * @param reqWidth
   * @param reqHeight
   * @return
   */
  public static Bitmap decodeSampledBitmapFromPath(String path,int reqWidth, int reqHeight)
  {
    Options options = new Options();
    options.inJustDecodeBounds=true;
    BitmapFactory.decodeFile(path,options);
    //计算采样率
    options.inSampleSize=caculateInSampleSize(options,reqWidth,reqHeight);
    options.inJustDecodeBounds=false;
    Bitmap bitmap=BitmapFactory.decodeFile(path, options);
    return bitmap;
  }
  //计算采样率
  private static int caculateInSampleSize(Options options, int reqWidth, int reqHeight) 
  {
    int width=options.outWidth; //原始图片宽
    int height=options.outHeight; //原始图片高
    int inSampleSize=1; //采样率
    if(width>reqWidth || height>reqHeight) //原始的宽比目标宽大，或者原始高比目标高大
    {
      int widthRadio=Math.round(width *1.0f/reqWidth);
      int heightRadio = Math.round(height * 1.0f / reqHeight);
      inSampleSize = Math.max(widthRadio, heightRadio);
    }
    return inSampleSize;
  }
  //获取ImageView的大小
  protected static ImageSize getImageViewSize(ImageView imageView) 
  {
    ImageSize imageSize = new ImageSize();
    DisplayMetrics metrics = imageView.getContext().getResources().getDisplayMetrics();
    LayoutParams lp = imageView.getLayoutParams();
    int width = imageView.getWidth();
    if (width <= 0) {
      width = lp.width;
    }
    if (width <= 0) {
      width = imageView.getMaxWidth();
    }
    if (width <= 0) {
      width = metrics.widthPixels;
    }
    int height = imageView.getHeight();
    if (height <= 0) {
      height = lp.height;
    }
    if (height <= 0) {
      height = imageView.getMaxHeight();
    }
    if (height <= 0) {
      height = metrics.heightPixels;
    }
    imageSize.width = width;
    imageSize.height = height;
    return imageSize;
  }
  //ImageView大小的封装类
  private static class ImageSize
  {
    int width;
    int height;
  }
}