在将图像上传到服务器之前，whatsapp / Instagram或其他如何压缩图像？ [英] How whatsapp/Instagram or other compresses the image before uploading it to server?

问题描述

我使用下面的方法在将图像上传到服务器之前压缩图像。

I used below method to compress image before uploading it to server.

总结下面的代码，最初我从手机/ SD卡拍摄图像，将其转换为位图并在位图上进行缩放和压缩。然后我将压缩的位图保存在磁盘上作为新位置的图像。

To summarize the below code, Initially i take image from phone/sdcard, convert it to bitmap and carryout scaling and compression on bitmap. then i save the compressed bitmap on the disk as image in new location.

此方法确实将图像从3mb - 5mb压缩到30-100kb。 （当我检查sdcard上的压缩图像大小时）

This method does compress the image from 3mb - 5mb to just in 30-100kb. (when i check the compressed image size on sdcard)

然后我发送新压缩的30-100kb图像，通过将其转换为位图字符串上传到服务器上（ by Base64.encodeToString（））

Then i send the newly compressed image of 30-100kb to upload on to the server by converting it to bitmap string ( by Base64.encodeToString() )

我认为它会正常工作。但是当我在服务器上检查上传的图像时，图像的大小与原始图像大小（压缩前的原始大小）相同，而不是压缩30-100kb大小的图像。

I thought it will work fine. But when i check the uploaded image on server, the size of image is same as original image size (original size before compressed) instead of compressed 30-100kb size image.

下面是代码：

public String compressImage(String imageUri)
  {
    String filePath = getRealPathFromURI(imageUri);
    Bitmap scaledBitmap = null;

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

    options.inJustDecodeBounds = true;
    Bitmap bmp = BitmapFactory.decodeFile(filePath, options);

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

    float maxHeight = 816.0f;
    float maxWidth = 612.0f;
    float imgRatio = actualWidth / actualHeight;
    float maxRatio = maxWidth / maxHeight;

    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;

        }
    }

    options.inSampleSize = calculateInSampleSize(options, actualWidth, actualHeight);

    options.inJustDecodeBounds = false;

    options.inPurgeable = true;
    options.inInputShareable = true;
    options.inTempStorage = new byte[16 * 1024];

    try {
        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));

    ExifInterface exif;
    try {
        exif = new ExifInterface(filePath);

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

    FileOutputStream out = null;
    String filename = getFilename();
    try {
        out = new FileOutputStream(filename);
        scaledBitmap.compress(Bitmap.CompressFormat.JPEG, 80, out);

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

public String getFilename() {
File file = new File(Environment.getExternalStorageDirectory().getPath(), "MyFolder/Images");
if (!file.exists()) {
    file.mkdirs();
}
String uriSting = (file.getAbsolutePath() + "/" +  System.currentTimeMillis() + ".jpg");
    return uriSting;}

private String getRealPathFromURI(String contentURI) {
    Uri contentUri = Uri.parse(contentURI);
    Cursor cursor = getContentResolver().query(contentUri, null, null, null, null);
    if (cursor == null) {
        return contentUri.getPath();
    } else {
        cursor.moveToFirst();
        int index = cursor.getColumnIndex(MediaStore.Images.ImageColumns.DATA);
        return cursor.getString(index);
    }
}

public 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;

}

我在某处出错了在上面这段代码？有没有更好的方法来压缩图像。我想知道如何上传未压缩的图像（位图）而不是压缩的图像。

Am i going wrong somewhere in this above code ? Is there any better method to compress the image. I am wondering how can uncompressed image(bitmap) is getting uploaded instead of compressed one.

whatsapp / instagram / facebook如何在上传到服务器之前压缩图像。它有没有图书馆。谢谢。

How does the whatsapp/instagram/facebook compresses the image before uploading on to the server. Is there any library for it. Thank you.

推荐答案

试试这个 ：

Try this:

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);
        }
    }

}

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