Java 内存有效的图像处理方法？

我有一些代码可以拍摄两个图像，并将它们的中间部分合并到一个图像中。该代码可以工作，但占用了大量内存，因此在一些内存不足的设备上会出现故障

有什么方法可以提高代码的内存效率吗

代码

---

你可以试试压缩。尝试此有用的imagecompressor类，为方便起见复制并粘贴到此线程中：

java压缩器会将图片压缩到其大小的1/10左右，因此对于3mb图片，它将变成300kb。希望这能为你节省一些记忆

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

import timber.log.Timber;

//http://voidcanvas.com/whatsapp-like-image-compression-in-android/
public class ImageCompressor {

    public ImageCompressor() {}

    public static String compressImage(String imagePath, Context context) {
        Bitmap scaledBitmap = null;
        String filename = "compressed_" +imagePath.substring(imagePath.lastIndexOf("/")+1);

        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;
        Timber.e( "imagePath "+imagePath);
        Timber.e("filename "+filename);
        Bitmap bmp = BitmapFactory.decodeFile(imagePath, options);
        if (options == null) {
            Timber.e("zero bitmap");
        }
        int actualHeight = options.outHeight;
        int actualWidth = options.outWidth;
        float imgRatio = actualWidth / actualHeight;

        float maxHeight = actualHeight * 10/20;
        float maxWidth = actualWidth * 10/20;
        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(imagePath, 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(imagePath);

            int orientation = exif.getAttributeInt(
                    ExifInterface.TAG_ORIENTATION, 0);
            Timber.e("Exif: " + orientation);
            Matrix matrix = new Matrix();
            if (orientation == 6) {
                matrix.postRotate(90);
                Timber.e( "Exif: " + orientation);
            } else if (orientation == 3) {
                matrix.postRotate(180);
                Timber.e( "Exif: " + orientation);
            } else if (orientation == 8) {
                matrix.postRotate(270);
                Timber.e( "Exif: " + orientation);
            }
            scaledBitmap = Bitmap.createBitmap(scaledBitmap, 0, 0,
                    scaledBitmap.getWidth(), scaledBitmap.getHeight(), matrix,
                    true);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (NullPointerException e) {
            e.printStackTrace();
        }

        FileOutputStream out = null;

        try {

            out = context.openFileOutput(filename, Context.MODE_PRIVATE);
            scaledBitmap.compress(Bitmap.CompressFormat.JPEG, 90, out);

            out.close();

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
            return filename;
        }

    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;      }
        final float totalPixels = width * height;
        final float totalReqPixelsCap = reqWidth * reqHeight * 2;
        while (totalPixels / (inSampleSize * inSampleSize) > totalReqPixelsCap) {
            inSampleSize++;
        }
        return inSampleSize;
    }

}
}

导入android.content.Context；
导入android.graphics.Bitmap；
导入android.graphics.BitmapFactory；
导入android.graphics.Canvas；
导入android.graphics.Matrix；
导入android.graphics.Paint；
导入android.media.ExifInterface；
导入java.io.FileNotFoundException；
导入java.io.FileOutputStream；
导入java.io.IOException；
进口木材；
//http://voidcanvas.com/whatsapp-like-image-compression-in-android/
公共级图像压缩程序{
公共图像压缩程序（）{}
公共静态字符串压缩图像（字符串图像路径、上下文）{
位图缩放位图=空；
String filename=“compressed\”+imagePath.substring（imagePath.lastIndexOf（“/”）+1）；
BitmapFactory.Options=new-BitmapFactory.Options（）；
//通过将此字段设置为true，实际位图像素不会加载到内存中。只加载边界。如果
//如果您尝试在此处使用位图，将得到null。
options.inJustDecodeBounds=true；
木材。e（“imagePath”+imagePath）；
e（“文件名”+文件名）；
位图bmp=BitmapFactory.decodeFile（图像路径，选项）；
如果（选项==null）{
Timber.e（“零位图”）；
}
int实际高度=options.outHeight；
int actualWidth=options.outWidth；
浮动高度=实际宽度/实际高度；
浮动最大高度=实际高度*10/20；
浮动最大宽度=实际宽度*10/20；
浮点最大比值=最大宽度/最大高度；
//设置宽度和高度值以保持图像的纵横比
如果（实际高度>最大高度| |实际宽度>最大宽度）{
if（imgRatiomaxRatio）{
imgRatio=最大宽度/实际宽度；
实际高度=（int）（imgRatio*实际高度）；
实际宽度=（int）最大宽度；
}否则{
实际高度=（int）最大高度；
实际宽度=（int）最大宽度；
}
}
//设置inSampleSize值允许加载原始图像的缩小版本
options.inSampleSize=calculateInSampleSize（选项、实际宽度、实际高度）；
//inJustDecodeBounds设置为false以加载实际位图
options.inJustDecodeBounds=false；
//此选项允许android在内存不足时声明位图内存
options.inpurgable=true；
options.inInputShareable=true；
options.inTempStorage=新字节[16*1024]；
试一试{
//从位图路径加载位图
bmp=BitmapFactory.decodeFile（图像路径，选项）；
}捕获（OutOfMemoryError异常）{
异常。printStackTrace（）；
}
试一试{
scaledbimat=Bitmap.createBitmap（实际宽度、实际高度、Bitmap.Config.ARGB_8888）；
}捕获（OutOfMemoryError异常）{
异常。printStackTrace（）；
}
浮动比率=实际宽度/（浮动）选项。向外宽度；
浮动比率=实际高度/（浮动）选项。超出高度；
浮动中间点x=实际宽度/2.0f；
浮动中间Y=实际高度/2.0f；
矩阵scaleMatrix=新矩阵（）；
scaleMatrix.setScale（ratioX、ratioY、middleX、middleY）；
画布画布=新画布（缩放位图）；
canvas.setMatrix（scaleMatrix）；
drawBitmap（bmp，middleX-bmp.getWidth（）/2，middleY-bmp.getHeight（）/2，新绘制（Paint.FILTER_位图_标志））；
//检查图像的旋转并正确显示
出口接口；
试一试{
exif=新的ExifInterface（imagePath）；
int-orientation=exif.getAttributeInt(
ExiFinInterface.TAG_方向，0）；
木材.e（“进出口银行：+方向”）；
矩阵=新矩阵（）；
如果（方向==6）{
矩阵旋转后（90）；
木材.e（“进出口银行：+方向”）；
}否则如果（方向==3）{
矩阵旋转后（180）；
木材.e（“进出口银行：+方向”）；
}否则如果（方向==8）{
矩阵旋转后（270）；
木材.e（“进出口银行：+方向”）；
}
scaledBitmap=Bitmap.createBitmap（scaledBitmap，0,0，
scaledBitmap.getWidth（），scaledBitmap.getHeight（），矩阵，
正确的）；
}捕获（IOE异常）{
e、 printStackTrace（）；
}捕获（NullPointerException e）{
e、 printStackTrace（）；
}
FileOutputStream out=null；
试一试{
out=context.openFileOutput（文件名，context.MODE\u PRIVATE）；
scaledBitmap.compress（Bitmap.CompressFormat.JPEG，90，out）；
out.close（）；
}catch（filenotfounde异常）{
e、 printStackTrace（）；
}捕获（IOE异常）{
e、 printStackTrace（）；
}
返回文件名；
}
公共静态int-calculateInSampleSize（BitmapFactory.Options选项、int-reqWidth、int-reqHeight）{
最终内部高度=options.outHeight；
最终int w
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 java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

import timber.log.Timber;

//http://voidcanvas.com/whatsapp-like-image-compression-in-android/
public class ImageCompressor {

    public ImageCompressor() {}

    public static String compressImage(String imagePath, Context context) {
        Bitmap scaledBitmap = null;
        String filename = "compressed_" +imagePath.substring(imagePath.lastIndexOf("/")+1);

        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;
        Timber.e( "imagePath "+imagePath);
        Timber.e("filename "+filename);
        Bitmap bmp = BitmapFactory.decodeFile(imagePath, options);
        if (options == null) {
            Timber.e("zero bitmap");
        }
        int actualHeight = options.outHeight;
        int actualWidth = options.outWidth;
        float imgRatio = actualWidth / actualHeight;

        float maxHeight = actualHeight * 10/20;
        float maxWidth = actualWidth * 10/20;
        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(imagePath, 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(imagePath);

            int orientation = exif.getAttributeInt(
                    ExifInterface.TAG_ORIENTATION, 0);
            Timber.e("Exif: " + orientation);
            Matrix matrix = new Matrix();
            if (orientation == 6) {
                matrix.postRotate(90);
                Timber.e( "Exif: " + orientation);
            } else if (orientation == 3) {
                matrix.postRotate(180);
                Timber.e( "Exif: " + orientation);
            } else if (orientation == 8) {
                matrix.postRotate(270);
                Timber.e( "Exif: " + orientation);
            }
            scaledBitmap = Bitmap.createBitmap(scaledBitmap, 0, 0,
                    scaledBitmap.getWidth(), scaledBitmap.getHeight(), matrix,
                    true);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (NullPointerException e) {
            e.printStackTrace();
        }

        FileOutputStream out = null;

        try {

            out = context.openFileOutput(filename, Context.MODE_PRIVATE);
            scaledBitmap.compress(Bitmap.CompressFormat.JPEG, 90, out);

            out.close();

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
            return filename;
        }

    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;      }
        final float totalPixels = width * height;
        final float totalReqPixelsCap = reqWidth * reqHeight * 2;
        while (totalPixels / (inSampleSize * inSampleSize) > totalReqPixelsCap) {
            inSampleSize++;
        }
        return inSampleSize;
    }

}
}