我有一些代码需要两个图像，并将它们的中间部分合并为一个图像。代码可以工作，但是使用了相当多的内存，因此在一些没有足够内存的设备上会失败。
有没有办法让这段代码更节省内存？
private void convertImages(){
ImageView imageView = (ImageView) findViewById(R.id.imageView);
File leftFile = new File(Environment.getExternalStorageDirectory(), "images/left.jpg");
File rightFile = new File(Environment.getExternalStorageDirectory(), "images/right.jpg");
Bitmap left = BitmapFactory.decodeFile(leftFile.getAbsolutePath());
Bitmap right = BitmapFactory.decodeFile(rightFile.getAbsolutePath());
Rect srcRect = new Rect( (int)(left.getWidth()*0.25), 0, (int)(left.getWidth()*0.75), left.getHeight() );
Rect dstRectLeft = new Rect( 0, 0, (int)(srcRect.width()/2), srcRect.height() );
Rect dstRectRight = new Rect( (int)(srcRect.width()/2), 0, srcRect.width(), srcRect.height() );
Bitmap outBitmap = Bitmap.createBitmap(srcRect.width(), srcRect.height(), Bitmap.Config.ARGB_8888);
Canvas outCanvas = new Canvas(outBitmap);
outCanvas.drawBitmap(left, srcRect, dstRectLeft, null);
outCanvas.drawBitmap(right, srcRect, dstRectRight, null);
imageView.setImageBitmap( outBitmap );
}
答案 0 :(得分：0)
您可以尝试压缩。试试这个有用的imagecompressor类，复制并粘贴到这个主题：
Android: Compressing images creates black borders on left and top margin
压缩器java会将你的图片压缩到大小的1/10，因此对于3mb的图片，它将变成300kb。希望这能为你节省一些时间。
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;
}
}
}
答案 1 :(得分：0)
你可以使用Bitmap.createScaledBitmap（src，dstWidth，dstHeight，filter）;缩小位图的方法，使其尺寸更小