ANDROID图片压缩代码

import java.io.FileDescriptor;
import java.io.FileInputStream;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;

/**
 * 图片处理类   压缩
 * 
 * @author Administrator
 * 
 */
public class ImageUtil {
    /**
     * get Bitmap
     * 
     * @param imgPath
     * @param minSideLength
     * @param maxNumOfPixels
     * @return
     */
    public static Bitmap getBitmap(String imgPath, int minSideLength,
            int maxNumOfPixels) {
        if (imgPath == null || imgPath.length() == 0)
            return null;

        try {
            FileDescriptor fd = new FileInputStream(imgPath).getFD();
            BitmapFactory.Options options = new BitmapFactory.Options();
            options.inJustDecodeBounds = true;
            // BitmapFactory.decodeFile(imgFile, options);
            BitmapFactory.decodeFileDescriptor(fd, null, options);

            options.inSampleSize = computeSampleSize(options,
                    minSideLength, maxNumOfPixels);
            try {
                // 这里一定要将其设置回false，因为之前我们将其设置成了true
                // 设置inJustDecodeBounds为true后，decodeFile并不分配空间，即，BitmapFactory解码出来的Bitmap为Null,但可计算出原始图片的长度和宽度
                options.inJustDecodeBounds = false;

                Bitmap bmp = BitmapFactory.decodeFile(imgPath, options);
                return bmp == null ? null : bmp;
            } catch (OutOfMemoryError err) {
                return null;
            }
        } catch (Exception e) {
            return null;
        }
    }

    /**
     * compute Sample Size
     * 
     * @param options
     * @param minSideLength
     * @param maxNumOfPixels
     * @return
     */
    private static  int computeSampleSize(BitmapFactory.Options options,
            int minSideLength, int maxNumOfPixels) {
        int initialSize = computeInitialSampleSize(options, minSideLength,
                maxNumOfPixels);

        int roundedSize;
        if (initialSize <= 8) {
            roundedSize = 1;
            while (roundedSize < initialSize) {
                roundedSize <<= 1;
            }
        } else {
            roundedSize = (initialSize + 7) / 8 * 8;
        }

        return roundedSize;
    }

    /**
     * compute Initial Sample Size
     * 
     * @param options
     * @param minSideLength
     * @param maxNumOfPixels
     * @return
     */
    private static  int computeInitialSampleSize(BitmapFactory.Options options,
            int minSideLength, int maxNumOfPixels) {
        double w = options.outWidth;
        double h = options.outHeight;

        // 上下限范围
        int lowerBound = (maxNumOfPixels == -1) ? 1 : (int) Math.ceil(Math
                .sqrt(w * h / maxNumOfPixels));
        int upperBound = (minSideLength == -1) ? 128 : (int) Math.min(
                Math.floor(w / minSideLength), Math.floor(h / minSideLength));

        if (upperBound < lowerBound) {
            // return the larger one when there is no overlapping zone.
            return lowerBound;
        }

        if ((maxNumOfPixels == -1) && (minSideLength == -1)) {
            return 1;
        } else if (minSideLength == -1) {
            return lowerBound;
        } else {
            return upperBound;
        }
    }
}