ImageUtil.java

package com.llf.basemodel.utils;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.media.ExifInterface;
import android.net.Uri;

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

/**
 * Created by llf on 2017/3/6.
 * 图片压缩
 */

public class ImageUtil {
    private ImageUtil() {

    }

    /**
     * 获取压缩后bitmap
     * @param context
     * @param imageUri
     * @param maxWidth
     * @param maxHeight
     * @return
     */
    static Bitmap getScaledBitmap(Context context, Uri imageUri, float maxWidth, float maxHeight) {
        String filePath = FileUtil.getRealPathFromURI(context, imageUri);
        Bitmap scaledBitmap = null;

        BitmapFactory.Options options = new BitmapFactory.Options();

        //by setting this field as true, the actual bitmap pixels are not loaded in the memory. Just the bounds are loaded. If
        //you try the use the bitmap here, you will get null.
        options.inJustDecodeBounds = true;
        Bitmap bmp = BitmapFactory.decodeFile(filePath, options);

        int actualHeight = options.outHeight;
        int actualWidth = options.outWidth;

        float imgRatio = (float)actualWidth / actualHeight;
        float maxRatio = maxWidth / maxHeight;

        //width and height values are set maintaining the aspect ratio of the image
        if (actualHeight > maxHeight || actualWidth > maxWidth) {
            if (imgRatio < maxRatio) {
                imgRatio = maxHeight / actualHeight; actualWidth = (int) (imgRatio * actualWidth);
                actualHeight = (int) maxHeight;
            } else if (imgRatio > maxRatio) {
                imgRatio = maxWidth / actualWidth;
                actualHeight = (int) (imgRatio * actualHeight);
                actualWidth = (int) maxWidth;
            } else {
                actualHeight = (int) maxHeight;
                actualWidth = (int) maxWidth;
            }
        }

        //setting inSampleSize value allows to load a scaled down version of the original image
        options.inSampleSize = calculateInSampleSize(options, actualWidth, actualHeight);

        //inJustDecodeBounds set to false to load the actual bitmap
        options.inJustDecodeBounds = false;

        //this options allow android to claim the bitmap memory if it runs low on memory
        options.inPurgeable = true;
        options.inInputShareable = true;
        options.inTempStorage = new byte[16 * 1024];

        try {
            //load the bitmap from its path
            bmp = BitmapFactory.decodeFile(filePath, options);
        } catch (OutOfMemoryError exception) {
            exception.printStackTrace();
        }
        try {
            scaledBitmap = Bitmap.createBitmap(actualWidth, actualHeight, Bitmap.Config.ARGB_8888);
        } catch (OutOfMemoryError exception) {
            exception.printStackTrace();
        }

        float ratioX = actualWidth / (float) options.outWidth;
        float ratioY = actualHeight / (float) options.outHeight;
        float middleX = actualWidth / 2.0f;
        float middleY = actualHeight / 2.0f;

        Matrix scaleMatrix = new Matrix();
        scaleMatrix.setScale(ratioX, ratioY, middleX, middleY);

        Canvas canvas = new Canvas(scaledBitmap);
        canvas.setMatrix(scaleMatrix);
        canvas.drawBitmap(bmp, middleX - bmp.getWidth() / 2, middleY - bmp.getHeight() / 2, new Paint(Paint.FILTER_BITMAP_FLAG));

        //check the rotation of the image and display it properly
        ExifInterface exif;
        try {
            exif = new ExifInterface(filePath);
            int orientation = exif.getAttributeInt(ExifInterface.TAG_ORIENTATION, 0);
            Matrix matrix = new Matrix();
            if (orientation == 6) {
                matrix.postRotate(90);
            } else if (orientation == 3) {
                matrix.postRotate(180);
            } else if (orientation == 8) {
                matrix.postRotate(270);
            }
            scaledBitmap = Bitmap.createBitmap(scaledBitmap, 0, 0,
                    scaledBitmap.getWidth(), scaledBitmap.getHeight(),
                    matrix, true);
        } catch (IOException e) {
            e.printStackTrace();
        }

        return scaledBitmap;
    }

    /**
     * 压缩图片
     * @param context
     * @param imageUri
     * @param maxWidth
     * @param maxHeight
     * @param compressFormat
     * @param quality
     * @param parentPath
     * @return
     */
    static File compressImage(Context context, Uri imageUri, float maxWidth, float maxHeight, Bitmap.CompressFormat compressFormat, int quality, String parentPath) {
        FileOutputStream out = null;
        String filename = generateFilePath(context, parentPath, imageUri, compressFormat.name().toLowerCase());
        try {
            out = new FileOutputStream(filename);

            //write the compressed bitmap at the destination specified by filename.
            ImageUtil.getScaledBitmap(context, imageUri, maxWidth, maxHeight).compress(compressFormat, quality, out);

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } finally {
            try {
                if (out != null) {
                    out.close();
                }
            } catch (IOException ignored) {
            }
        }

        return new File(filename);
    }

    private static String generateFilePath(Context context, String parentPath, Uri uri, String extension) {
        File file = new File(parentPath);
        if (!file.exists()) {
            file.mkdirs();
        }
        return file.getAbsolutePath() + File.separator + FileUtil.splitFileName(FileUtil.getFileName(context, uri))[0] + "." + extension;
    }

    private 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;
        }

        final float totalPixels = width * height;
        final float totalReqPixelsCap = reqWidth * reqHeight * 2;

        while (totalPixels / (inSampleSize * inSampleSize) > totalReqPixelsCap) {
            inSampleSize++;
        }

        return inSampleSize;
    }
}