如何在上传到服务器之前减小图像文件大小

Question

许多应用程序允许共享从图库中挑选的图像.

他们上传原始图片文件吗？这是1-3 MB？或者他们处理？

在任何情况下,我如何从文件路径中获取图像,通过降低分辨率来减小其大小,并将其保存在其他地方并尝试上传？

我试过了:

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);
}

但这是他们正确的方法吗？因为我在这里看到了答案compression operation takes rather big amount of time

Answer 1

我使用此功能在上传之前减小图像的大小,它将图像大小减小到接近200 KB并保持质量相对较好,您可以通过更改REQUIRED_SIZE和inSampleSize来修改它以实现您的目的:

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:我在此函数中调整大小并覆盖原始文件图像,您也可以将其写入另一个文件.

我希望它可以帮助你.

Answer 2

这很有效试试这个

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);
        }
    }

}

Answer 3

这是在内存中处理的解决方案，不需要在文件系统上实际生成文件。

从某个片段中，在用户选择图像文件后：

@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;
}

谢谢：

• 将 uri 转换为位图：https : //stackoverflow.com/a/4717740/2162226
• 缩放/调整大小步骤（来自此线程）：https : //stackoverflow.com/a/50192169/2162226
• 将字节 [] 保存到 Firebase：https ://stackoverflow.com/a/40886397/2162226

Answer 4

此代码减小尺寸图像

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;
    }

Answer 5

您可以使用这个名为Compressor的库。

压缩图像文件

val compressedImageFile = Compressor.compress(context, actualImageFile)
Compress Image File to specific destination
val compressedImageFile = Compressor.compress(context, actualImageFile) {
    default()
    destination(myFile)
}

定制压缩机

使用默认约束和它的自定义部分

  val compressedImageFile = 
       Compressor.compress(context, actualImageFile) {
        default(width = 640, format = Bitmap.CompressFormat.WEBP)
    }

完全自定义约束

val compressedImageFile = Compressor.compress(context, actualImageFile) {
    resolution(1280, 720)
    quality(80)
    format(Bitmap.CompressFormat.WEBP)
    size(2_097_152) // 2 MB
}

使用自己的自定义约束

class MyLowerCaseNameConstraint: Constraint {
    override fun isSatisfied(imageFile: File): Boolean {
        return imageFile.name.all { it.isLowerCase() }
    }

    override fun satisfy(imageFile: File): File {
        val destination = File(imageFile.parent, imageFile.name.toLowerCase())
        imageFile.renameTo(destination)
        return destination
    }
}

val compressedImageFile = Compressor.compress(context, actualImageFile) {
    constraint(MyLowerCaseNameConstraint()) // your own constraint
    quality(80) // combine with compressor constraint
    format(Bitmap.CompressFormat.WEBP)
}

创建 Kotlin 扩展 -

fun Compression.lowerCaseName() {
    constraint(MyLowerCaseNameConstraint())
}

val compressedImageFile = Compressor.compress(context, actualImageFile) {
    lowerCaseName() // your own extension
    quality(80) // combine with compressor constraint
    format(Bitmap.CompressFormat.WEBP)
}

使用 Kotlin 协程压缩图像 -

// e.g calling from activity lifecycle scope
lifecycleScope.launch {
    val compressedImageFile = Compressor.compress(context, actualImageFile)
}

// calling from global scope
GlobalScope.launch {
    val compressedImageFile = Compressor.compress(context, actualImageFile)
}

在主线程中运行 Compressor -

val compressedImageFile = Compressor.compress(context, actualImageFile, Dispatchers.Main)