サーバーにアップロードする前に画像ファイルのサイズを縮小する方法

Question 1

多くのアプリケーションでは、ギャラリーから選択した画像を共有できます。

元の画像ファイルをアップロードしますか？1〜3 mbのようなものはどれですか？それとも彼らは処理しますか？

いずれにせよ、ファイルパスから画像を取得し、解像度を下げてサイズを縮小し、他の場所に保存してアップロードを試みるにはどうすればよいですか？

私は試した：

Bitmap photo = decodeSampledBitmapFromFile(filePath, DESIRED_WIDTH,
                    DESIRED_HEIGHT);

FileOutputStream out = new FileOutputStream(filePath);
photo.compress(Bitmap.CompressFormat.JPEG, 100, out);

public static Bitmap decodeSampledBitmapFromFile(String path, int reqWidth,
        int reqHeight) {

    final BitmapFactory.Options options = new BitmapFactory.Options();
    options.inJustDecodeBounds = true;
    BitmapFactory.decodeFile(path, options);

    final int height = options.outHeight;
    final int width = options.outWidth;
    options.inPreferredConfig = Bitmap.Config.ARGB_8888;
    int inSampleSize = 1;

    if (height > reqHeight) {
        inSampleSize = Math.round((float) height / (float) reqHeight);
    }
    int expectedWidth = width / inSampleSize;

    if (expectedWidth > reqWidth) {
        inSampleSize = Math.round((float) width / (float) reqWidth);
    }
    options.inSampleSize = inSampleSize;
    options.inJustDecodeBounds = false;
    return BitmapFactory.decodeFile(path, options);
}

しかし、これは彼らが行う正しい方法ですか？私はここで示唆する答えを見たのでcompression operation takes rather big amount of time

Question 2

この関数を使用して、アップロードする前に画像のサイズを縮小します。画像のサイズを200 KB近くに縮小し、品質を比較的良好に保ちます。REQUIRED_SIZEとinSampleSizeを変更することで、目的に合わせて変更できます。

public File saveBitmapToFile(File file){
    try {

        // BitmapFactory options to downsize the image
        BitmapFactory.Options o = new BitmapFactory.Options();
        o.inJustDecodeBounds = true;
        o.inSampleSize = 6;
        // factor of downsizing the image

        FileInputStream inputStream = new FileInputStream(file);
        //Bitmap selectedBitmap = null;
        BitmapFactory.decodeStream(inputStream, null, o);
        inputStream.close();

        // The new size we want to scale to
        final int REQUIRED_SIZE=75;

        // Find the correct scale value. It should be the power of 2.
        int scale = 1;
        while(o.outWidth / scale / 2 >= REQUIRED_SIZE &&
                        o.outHeight / scale / 2 >= REQUIRED_SIZE) {
            scale *= 2;
        }

        BitmapFactory.Options o2 = new BitmapFactory.Options();
        o2.inSampleSize = scale;
        inputStream = new FileInputStream(file);

        Bitmap selectedBitmap = BitmapFactory.decodeStream(inputStream, null, o2);
        inputStream.close();

        // here i override the original image file
        file.createNewFile();
        FileOutputStream outputStream = new FileOutputStream(file);

        selectedBitmap.compress(Bitmap.CompressFormat.JPEG, 100 , outputStream);

        return file;
    } catch (Exception e) {
        return null;
    }
}

注意：この関数で元のファイル画像のサイズを変更して上書きします。別のファイルに書き込むこともできます。

お役に立てば幸いです。

Question 3

これはうまく機能していますこれを試してください

private String decodeFile(String path,int DESIREDWIDTH, int DESIREDHEIGHT) {
        String strMyImagePath = null;
        Bitmap scaledBitmap = null;

        try {
            // Part 1: Decode image
            Bitmap unscaledBitmap = ScalingUtilities.decodeFile(path, DESIREDWIDTH, DESIREDHEIGHT, ScalingLogic.FIT);

            if (!(unscaledBitmap.getWidth() <= DESIREDWIDTH && unscaledBitmap.getHeight() <= DESIREDHEIGHT)) {
                // Part 2: Scale image
                scaledBitmap = ScalingUtilities.createScaledBitmap(unscaledBitmap, DESIREDWIDTH, DESIREDHEIGHT, ScalingLogic.FIT);
            } else {
                unscaledBitmap.recycle();
                return path;
            }

            // Store to tmp file

            String extr = Environment.getExternalStorageDirectory().toString();
            File mFolder = new File(extr + "/TMMFOLDER");
            if (!mFolder.exists()) {
                mFolder.mkdir();
            }

            String s = "tmp.png";

            File f = new File(mFolder.getAbsolutePath(), s);

            strMyImagePath = f.getAbsolutePath();
            FileOutputStream fos = null;
            try {
                fos = new FileOutputStream(f);
                scaledBitmap.compress(Bitmap.CompressFormat.JPEG, 75, fos);
                fos.flush();
                fos.close();
            } catch (FileNotFoundException e) {

                e.printStackTrace();
            } catch (Exception e) {

                e.printStackTrace();
            }

            scaledBitmap.recycle();
        } catch (Throwable e) {
        }

        if (strMyImagePath == null) {
            return path;
        }
        return strMyImagePath;

    }

ScalingUtilities.java

import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.BitmapFactory;
import android.graphics.BitmapFactory.Options;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;

/**
 * Class containing static utility methods for bitmap decoding and scaling
 *
 * @author 
 */
public class ScalingUtilities {

    /**
     * Utility function for decoding an image resource. The decoded bitmap will
     * be optimized for further scaling to the requested destination dimensions
     * and scaling logic.
     *
     * @param res The resources object containing the image data
     * @param resId The resource id of the image data
     * @param dstWidth Width of destination area
     * @param dstHeight Height of destination area
     * @param scalingLogic Logic to use to avoid image stretching
     * @return Decoded bitmap
     */
    public static Bitmap decodeResource(Resources res, int resId, int dstWidth, int dstHeight,
            ScalingLogic scalingLogic) {
        Options options = new Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeResource(res, resId, options);
        options.inJustDecodeBounds = false;
        options.inSampleSize = calculateSampleSize(options.outWidth, options.outHeight, dstWidth,
                dstHeight, scalingLogic);
        Bitmap unscaledBitmap = BitmapFactory.decodeResource(res, resId, options);

        return unscaledBitmap;
    }
    public static Bitmap decodeFile(String path, int dstWidth, int dstHeight,
            ScalingLogic scalingLogic) {
        Options options = new Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeFile(path, options);
        options.inJustDecodeBounds = false;
        options.inSampleSize = calculateSampleSize(options.outWidth, options.outHeight, dstWidth,
                dstHeight, scalingLogic);
        Bitmap unscaledBitmap = BitmapFactory.decodeFile(path, options);

        return unscaledBitmap;
    }

    /**
     * Utility function for creating a scaled version of an existing bitmap
     *
     * @param unscaledBitmap Bitmap to scale
     * @param dstWidth Wanted width of destination bitmap
     * @param dstHeight Wanted height of destination bitmap
     * @param scalingLogic Logic to use to avoid image stretching
     * @return New scaled bitmap object
     */
    public static Bitmap createScaledBitmap(Bitmap unscaledBitmap, int dstWidth, int dstHeight,
            ScalingLogic scalingLogic) {
        Rect srcRect = calculateSrcRect(unscaledBitmap.getWidth(), unscaledBitmap.getHeight(),
                dstWidth, dstHeight, scalingLogic);
        Rect dstRect = calculateDstRect(unscaledBitmap.getWidth(), unscaledBitmap.getHeight(),
                dstWidth, dstHeight, scalingLogic);
        Bitmap scaledBitmap = Bitmap.createBitmap(dstRect.width(), dstRect.height(),
                Config.ARGB_8888);
        Canvas canvas = new Canvas(scaledBitmap);
        canvas.drawBitmap(unscaledBitmap, srcRect, dstRect, new Paint(Paint.FILTER_BITMAP_FLAG));

        return scaledBitmap;
    }

    /**
     * ScalingLogic defines how scaling should be carried out if source and
     * destination image has different aspect ratio.
     *
     * CROP: Scales the image the minimum amount while making sure that at least
     * one of the two dimensions fit inside the requested destination area.
     * Parts of the source image will be cropped to realize this.
     *
     * FIT: Scales the image the minimum amount while making sure both
     * dimensions fit inside the requested destination area. The resulting
     * destination dimensions might be adjusted to a smaller size than
     * requested.
     */
    public static enum ScalingLogic {
        CROP, FIT
    }

    /**
     * Calculate optimal down-sampling factor given the dimensions of a source
     * image, the dimensions of a destination area and a scaling logic.
     *
     * @param srcWidth Width of source image
     * @param srcHeight Height of source image
     * @param dstWidth Width of destination area
     * @param dstHeight Height of destination area
     * @param scalingLogic Logic to use to avoid image stretching
     * @return Optimal down scaling sample size for decoding
     */
    public static int calculateSampleSize(int srcWidth, int srcHeight, int dstWidth, int dstHeight,
            ScalingLogic scalingLogic) {
        if (scalingLogic == ScalingLogic.FIT) {
            final float srcAspect = (float)srcWidth / (float)srcHeight;
            final float dstAspect = (float)dstWidth / (float)dstHeight;

            if (srcAspect > dstAspect) {
                return srcWidth / dstWidth;
            } else {
                return srcHeight / dstHeight;
            }
        } else {
            final float srcAspect = (float)srcWidth / (float)srcHeight;
            final float dstAspect = (float)dstWidth / (float)dstHeight;

            if (srcAspect > dstAspect) {
                return srcHeight / dstHeight;
            } else {
                return srcWidth / dstWidth;
            }
        }
    }

    /**
     * Calculates source rectangle for scaling bitmap
     *
     * @param srcWidth Width of source image
     * @param srcHeight Height of source image
     * @param dstWidth Width of destination area
     * @param dstHeight Height of destination area
     * @param scalingLogic Logic to use to avoid image stretching
     * @return Optimal source rectangle
     */
    public static Rect calculateSrcRect(int srcWidth, int srcHeight, int dstWidth, int dstHeight,
            ScalingLogic scalingLogic) {
        if (scalingLogic == ScalingLogic.CROP) {
            final float srcAspect = (float)srcWidth / (float)srcHeight;
            final float dstAspect = (float)dstWidth / (float)dstHeight;

            if (srcAspect > dstAspect) {
                final int srcRectWidth = (int)(srcHeight * dstAspect);
                final int srcRectLeft = (srcWidth - srcRectWidth) / 2;
                return new Rect(srcRectLeft, 0, srcRectLeft + srcRectWidth, srcHeight);
            } else {
                final int srcRectHeight = (int)(srcWidth / dstAspect);
                final int scrRectTop = (int)(srcHeight - srcRectHeight) / 2;
                return new Rect(0, scrRectTop, srcWidth, scrRectTop + srcRectHeight);
            }
        } else {
            return new Rect(0, 0, srcWidth, srcHeight);
        }
    }

    /**
     * Calculates destination rectangle for scaling bitmap
     *
     * @param srcWidth Width of source image
     * @param srcHeight Height of source image
     * @param dstWidth Width of destination area
     * @param dstHeight Height of destination area
     * @param scalingLogic Logic to use to avoid image stretching
     * @return Optimal destination rectangle
     */
    public static Rect calculateDstRect(int srcWidth, int srcHeight, int dstWidth, int dstHeight,
            ScalingLogic scalingLogic) {
        if (scalingLogic == ScalingLogic.FIT) {
            final float srcAspect = (float)srcWidth / (float)srcHeight;
            final float dstAspect = (float)dstWidth / (float)dstHeight;

            if (srcAspect > dstAspect) {
                return new Rect(0, 0, dstWidth, (int)(dstWidth / srcAspect));
            } else {
                return new Rect(0, 0, (int)(dstHeight * srcAspect), dstHeight);
            }
        } else {
            return new Rect(0, 0, dstWidth, dstHeight);
        }
    }

}

Question 4

このコードは画像のサイズを縮小します

private Bitmap compressImage(Bitmap image) {

        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        image.compress(Bitmap.CompressFormat.JPEG, 100, baos);//Compression quality, here 100 means no compression, the storage of compressed data to baos
        int options = 90;
        while (baos.toByteArray().length / 1024 > 400) {  //Loop if compressed picture is greater than 400kb, than to compression
            baos.reset();//Reset baos is empty baos
            image.compress(Bitmap.CompressFormat.JPEG, options, baos);//The compression options%, storing the compressed data to the baos
            options -= 10;//Every time reduced by 10
        }
        ByteArrayInputStream isBm = new ByteArrayInputStream(baos.toByteArray());//The storage of compressed data in the baos to ByteArrayInputStream
        Bitmap bitmap = BitmapFactory.decodeStream(isBm, null, null);//The ByteArrayInputStream data generation
        return bitmap;
    }

Question 5

これは、メモリ内で処理され、ファイルシステム上で実際にファイルを生成する必要がないソリューションです。

一部のフラグメントから、ユーザーが画像ファイルを選択した後：

@Override
public void onActivityResult(int requestCode, int resultCode, Intent imageReturnedIntent) {
    super.onActivityResult(requestCode, resultCode, imageReturnedIntent);

    if (imageReturnedIntent == null
            || imageReturnedIntent.getData() == null) {
        return;
    }

    // aiming for ~500kb max. assumes typical device image size is around 2megs
    int scaleDivider = 4; 


    try {

        // 1. Convert uri to bitmap
        Uri imageUri = imageReturnedIntent.getData();
        Bitmap fullBitmap = MediaStore.Images.Media.getBitmap(getActivity().getContentResolver(), imageUri);

        // 2. Get the downsized image content as a byte[]
        int scaleWidth = fullBitmap.getWidth() / scaleDivider;
        int scaleHeight = fullBitmap.getHeight() / scaleDivider;
        byte[] downsizedImageBytes =
                getDownsizedImageBytes(fullBitmap, scaleWidth, scaleHeight);

        // 3. Upload the byte[]; Eg, if you are using Firebase
        StorageReference storageReference =
                FirebaseStorage.getInstance().getReference("/somepath");

        storageReference.putBytes(downsizedImageBytes);
    }
    catch (IOException ioEx) {
        ioEx.printStackTrace();
    }
}

public byte[] getDownsizedImageBytes(Bitmap fullBitmap, int scaleWidth, int scaleHeight) throws IOException {

    Bitmap scaledBitmap = Bitmap.createScaledBitmap(fullBitmap, scaleWidth, scaleHeight, true);

    // 2. Instantiate the downsized image content as a byte[]
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    scaledBitmap.compress(Bitmap.CompressFormat.JPEG, 100, baos);
    byte[] downsizedImageBytes = baos.toByteArray();

    return downsizedImageBytes;
}

おかげで：

uriをビットマップに変換します：https：//stackoverflow.com/a/4717740/2162226
スケーリング/サイズ変更のステップ（このスレッドから）：https：//stackoverflow.com/a/50192169/2162226
byte []をFirebaseに保存します：https：//stackoverflow.com/a/40886397/2162226

Question 6

これが私の解決策です

/*
* This procedure will replace the original image
* So you need to do a tmp copy to send before reduce
*/
public static boolean reduceImage(String path, long maxSize) {
    File img = new File(path);
    boolean result = false;
    BitmapFactory.Options options = new BitmapFactory.Options();
    Bitmap bitmap = null;
    options.inSampleSize=1;
    while (img.length()>maxSize) {
        options.inSampleSize = options.inSampleSize+1;
        bitmap = BitmapFactory.decodeFile(path, options);
        img.delete();
        try
            {
                FileOutputStream fos = new FileOutputStream(path);
                img.compress(path.toLowerCase().endsWith("png")?
                                Bitmap.CompressFormat.PNG:
                                Bitmap.CompressFormat.JPEG, 100, fos);
                fos.close();
                result = true;
             }catch (Exception errVar) { 
                errVar.printStackTrace(); 
             }
    };
    return result;
}

編集他のプロシージャコールを削除しました

Question 7

kotlinでiamが使用しているメソッドは次のとおりです。

注：3つの画像で試してみました。それぞれが6 mbで、1回の呼び出しで

 private fun Bitmap.compress(cacheDir: File, f_name: String): File? {
    val f = File(cacheDir, "user$f_name.jpg")
    f.createNewFile()
    ByteArrayOutputStream().use { stream ->
        compress(Bitmap.CompressFormat.JPEG, 70, stream)
        val bArray = stream.toByteArray()
        FileOutputStream(f).use { os -> os.write(bArray) }
    }//stream
    return f
}

Question 8

@MBHの回答には、ファイルのピクセル数が6Xを超える場合に、whileループがバイパスされる可能性のある、奇妙で不必要な結果を取得する方法がありますREQUIRED_SIZE = 75;。o.inSampleSize = 6;これが原因であり、許容される軸方向ピクセル数（6 * 75 = 450）の畳み込みにのみ成功します。以下は、MBHの回答の改良版であり、ピクセルだけでなくストレージサイズによっても調整するオプションも含まれています。

//This is the number of pixels that the width and height of the image will be allotted
//Note that the number of pixels implies (but does not exclusively determine) the file size of the image
private int REQUIRED_SIZE = 720;
//Method allows image files to be compressed to a standard maximum size
public void saveBitmapToFile(){

    try {

        //Initialize BitmapFactory options to downsize the image
        BitmapFactory.Options o = new BitmapFactory.Options();
        //Image dimensions do not change with change in pixel density
        o.inJustDecodeBounds = true;

        //Retrieve file and decode into bitmap, then close the stream when decode complete
        FileInputStream inputStream = new FileInputStream(imageFile);
        BitmapFactory.decodeStream(inputStream, null, o);
        inputStream.close();

        //Start with 1:1 scale size
        int scale = 1;

        while (o.outWidth / scale / 2 >= REQUIRED_SIZE && o.outHeight / scale / 2 >= REQUIRED_SIZE) {
            //Find the correct scale value. It should be the power of 2.
            scale *= 2;
        }

        //Create new Bitmap options instance to adjust the image scale...(1/2)
        BitmapFactory.Options o2 = new BitmapFactory.Options();
        o2.inSampleSize = scale;
        //...then apply with new input stream
        inputStream = new FileInputStream(imageFile);
        Bitmap selectedBitmap = BitmapFactory.decodeStream(inputStream, null, o2);
        inputStream.close();

        //Overwrite original file (type 'File') then compress the output file
        imageFile.createNewFile();
        FileOutputStream outputStream = new FileOutputStream(imageFile);
        selectedBitmap.compress(Bitmap.CompressFormat.JPEG, 100, outputStream);

        //maxImageSize is arbitrary file size (byte) limit
        if(imageFile.length() < maxImageSize) {

            //Set image in place and get the uri
            imagePost.setImageURI(imageUri);

            //Reset in case decreased previously
            REQUIRED_SIZE = 720;

        } else {

            Toast.makeText(PostActivity.this, "Your image is " + (imageFile.length() - maxImageSize) / 1000 + "kb too large to upload. Reattempting...", Toast.LENGTH_LONG).show();

            REQUIRED_SIZE = REQUIRED_SIZE - 240;

            //Loop method until goal file size achieved
            saveBitmapToFile();

        }

    } catch (Exception ignored) {

    }

}

Question 9

約200KBに圧縮されたビットマップイメージを返すこのメソッドを使用します。必要なサイズのビットマップイメージを取得するように構成できます。

public static Bitmap scaleImage(Context context, Uri photoUri) throws IOException {
    InputStream is = context.getContentResolver().openInputStream(photoUri);
    BitmapFactory.Options dbo = new BitmapFactory.Options();
    dbo.inJustDecodeBounds = true;
    BitmapFactory.decodeStream(is, null, dbo);
    is.close();

    int rotatedWidth, rotatedHeight;
    int orientation = getOrientation(context, photoUri);

    if (orientation == 90 || orientation == 270) {
        rotatedWidth = dbo.outHeight;
        rotatedHeight = dbo.outWidth;
    } else {
        rotatedWidth = dbo.outWidth;
        rotatedHeight = dbo.outHeight;
    }

    Bitmap srcBitmap;
    is = context.getContentResolver().openInputStream(photoUri);
    if (rotatedWidth > MAX_IMAGE_DIMENSION || rotatedHeight > MAX_IMAGE_DIMENSION) {
        float widthRatio = ((float) rotatedWidth) / ((float) MAX_IMAGE_DIMENSION);
        float heightRatio = ((float) rotatedHeight) / ((float) MAX_IMAGE_DIMENSION);
        float maxRatio = Math.max(widthRatio, heightRatio);

        // Create the bitmap from file
        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inSampleSize = (int) maxRatio;
        srcBitmap = BitmapFactory.decodeStream(is, null, options);
    } else {
        srcBitmap = BitmapFactory.decodeStream(is);
    }
    is.close();

    /*
     * if the orientation is not 0 (or -1, which means we don't know), we
     * have to do a rotation.
     */
    if (orientation > 0) {
        Matrix matrix = new Matrix();
        matrix.postRotate(orientation);

        srcBitmap = Bitmap.createBitmap(srcBitmap, 0, 0, srcBitmap.getWidth(),
                srcBitmap.getHeight(), matrix, true);
    }

    String type = context.getContentResolver().getType(photoUri);
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    if (type.equals("image/png")) {
        srcBitmap.compress(Bitmap.CompressFormat.PNG, 100, baos);
    } else if (type.equals("image/jpg") || type.equals("image/jpeg")) {
        srcBitmap.compress(Bitmap.CompressFormat.JPEG, 100, baos);
    }
    byte[] bMapArray = baos.toByteArray();
    baos.close();
    return BitmapFactory.decodeByteArray(bMapArray, 0, bMapArray.length);
}