這是專案中用到的圖片工具類，記錄於此。

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Matrix;
import android.media.ExifInterface;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;

public class BitmapUtils {
    public static Bitmap getSmallBitmap(String filePath) {
        final BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        //inJustDecodeBounds設定為true，可以不把圖片讀到記憶體中,但依然可以計算出圖片的大小
        BitmapFactory.decodeFile(filePath, options);

        // Calculate inSampleSize
        options.inSampleSize = calculateInSampleSize(options, 480, 800);

        // Decode bitmap with inSampleSize set
        options.inJustDecodeBounds = false;
        //此時返回的就是已經被壓縮的bitmap。。可以用於顯示在介面上
        return BitmapFactory.decodeFile(filePath, options);
    }

    /**
     * 計算圖片的縮放值
     */
    public static int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
        final int height = options.outHeight;
        final int width = options.outWidth;
        int inSampleSize = 1;

        if (height > reqHeight || width > reqWidth) {
            final int heightRatio = Math.round((float) height / (float) reqHeight);
            final int widthRatio = Math.round((float) width / (float) reqWidth);
            inSampleSize = heightRatio < widthRatio ? heightRatio : widthRatio;
        }
        return inSampleSize;
    }

    /**
     * 壓縮圖片到指定位置(預設JPG格式)
     *
     * @param filePath   需要壓縮的圖片路徑
     * @param targetPath 壓縮後的圖片路徑
     * @param quality    圖片質量，0~100
     * @return 壓縮後的圖片路徑
     */
    public static String compressImage(String filePath, String targetPath, int quality) {
        Bitmap bm = getSmallBitmap(filePath);//獲取一定尺寸的圖片
        int degree = readPictureDegree(filePath);//獲取相片拍攝角度
        if (degree != 0) {//旋轉照片角度，防止頭像橫著顯示
            bm = rotateBitmap(bm, degree);
        }
        File outputFile = new File(targetPath);
        try {
            if (!outputFile.exists()) {
                outputFile.getParentFile().mkdirs();
                //outputFile.createNewFile();
            } else {
                outputFile.delete();
            }
            FileOutputStream out = new FileOutputStream(outputFile);
            bm.compress(Bitmap.CompressFormat.JPEG, quality, out);
        } catch (Exception e) {
        }
        return outputFile.getPath();
    }

    /**
     * 獲取照片角度
     *
     * @param path
     * @return
     */
    public static int readPictureDegree(String path) {
        int degree = 0;
        try {
            ExifInterface exifInterface = new ExifInterface(path);
            int orientation = exifInterface.getAttributeInt(
                    ExifInterface.TAG_ORIENTATION,
                    ExifInterface.ORIENTATION_NORMAL);
            switch (orientation) {
                case ExifInterface.ORIENTATION_ROTATE_90:
                    degree = 90;
                    break;
                case ExifInterface.ORIENTATION_ROTATE_180:
                    degree = 180;
                    break;
                case ExifInterface.ORIENTATION_ROTATE_270:
                    degree = 270;
                    break;
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        return degree;
    }

    /**
     * 旋轉照片
     *
     * @param bitmap
     * @param degress
     * @return
     */
    public static Bitmap rotateBitmap(Bitmap bitmap, int degress) {
        if (bitmap != null) {
            Matrix m = new Matrix();
            m.postRotate(degress);
            bitmap = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(),
                    bitmap.getHeight(), m, true);
            return bitmap;
        }
        return bitmap;
    }

}