Question

我想使用Android相机api以低分辨率捕捉图像，但是当我拍摄图像时，它将采用设备相机的默认分辨率。所以我想在拍摄时捕获低分辨率或小尺寸的图像或者我如何压缩在android中将大图像变成小尺寸？

Answer 1

您可以使用捕获的图像创建位图，如下所示：

Bitmap bitmap = Bitmap.createScaledBitmap(capturedImage, width, height, true);

您可以在此处指定要设置为ImageView的位图的宽度和高度。通过以编程方式读取不同设备的屏幕dpi，您还可以根据设备的屏幕dpi设置高度和宽度。

Answer 2

试试这个对我有用。

private String decodeFile(String path) {
        String strMyImagePath = null;
        Bitmap scaledBitmap = null;

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

            if (!(unscaledBitmap.getWidth() <= 800 && unscaledBitmap.getHeight() <= 800)) {
                // 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 + "/myTmpDir");
            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.PNG, 70, 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;

    }

公用事业类

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

使用Compressor（图像压缩库）。访问此link以获取代码文档

在gradle中添加依赖关系（应用级别）

依赖{ 编译'id.zelory：压缩器：2.1.0'}
要压缩图像，请使用以下方法之一：

（i）压缩图像文件：

File compressedImageFile = new Compressor(this).compressToFile(actualImageFile);

（ii）将图像文件压缩到位图：

Bitmap compressedImageBitmap = new Compressor(this).compressToBitmap(actualImageFile);

Answer 4

您可以像这样压缩图像位图。

ByteArrayOutputStream out = new ByteArrayOutputStream();
bitmap.compress(Bitmap.CompressFormat.PNG, 100, out);

此处100是图像质量，您可以更改图像格式以获得低分辨率图像。

Answer 5

我认为你问的是缩小图像尺寸：

    public Bitmap ShrinkBitmap(String file, int width, int height)
{
    BitmapFactory.Options bmpFactoryOptions = new BitmapFactory.Options();
    bmpFactoryOptions.inJustDecodeBounds = true;
    Bitmap bitmap = BitmapFactory.decodeFile(file, bmpFactoryOptions);

    int heightRatio = (int) Math.ceil(bmpFactoryOptions.outHeight / (float) height);
    int widthRatio = (int) Math.ceil(bmpFactoryOptions.outWidth / (float) width);

    if(heightRatio > 1 || widthRatio > 1)
    {
        if(heightRatio > widthRatio)
        {
            bmpFactoryOptions.inSampleSize = heightRatio;
        }
        else
        {
            bmpFactoryOptions.inSampleSize = widthRatio;
        }
    }

    bmpFactoryOptions.inJustDecodeBounds = false;
    bitmap = BitmapFactory.decodeFile(file, bmpFactoryOptions);
    return bitmap;
}

Answer 6

请查看我用于压缩图像的compressImage方法。

public static String compressImage(String imageUri, Activity activity) {
    String filename = "";
    try {
        String filePath = getRealPathFromURI(imageUri, activity);
        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.inDither = 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;
        if (scaledBitmap != null) {
            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);

            Matrix matrix = new Matrix();
            if (orientation == 6) {
                matrix.postRotate(90);

            } else if (orientation == 3) {
                matrix.postRotate(180);

            } else if (orientation == 8) {
                matrix.postRotate(270);

            }
            if (scaledBitmap != null) {
                scaledBitmap = Bitmap.createBitmap(scaledBitmap, 0, 0, scaledBitmap.getWidth(), scaledBitmap.getHeight(), matrix, true);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        FileOutputStream out;
        filename = getFilename(activity);
        try {
            out = new FileOutputStream(filename);
            if (scaledBitmap != null) {
                scaledBitmap.compress(Bitmap.CompressFormat.JPEG, 80, out);
            }

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

    return filename;
}

private 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;
}

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

Answer 7

只是你试试这个

byte[] data = null;
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    bi.compress(Bitmap.CompressFormat.JPEG, 100, baos);
    data = baos.toByteArray();

Answer 8

我以这种方式解决了这个问题，稍后我将改进代码

protected Void doInBackground(byte[]... data) {
        FileOutputStream outStream = null;

        // Write to Internal Storage
        try {
            File dir = new File (context.getFilesDir());
            dir.mkdirs();

            String fileName ="image.jpg";
            File outFile = new File(dir, fileName);
            outFile.setExecutable(true, false);
            outFile.setWritable(true, false);
            outStream = new FileOutputStream(outFile);
            outStream.write(data[0]);
            outStream.flush();
            outStream.close();
            InputStream in = new FileInputStream(context.getFilesDir()+"image.jpg");
            Bitmap bm2 = BitmapFactory.decodeStream(in);
            OutputStream stream = new FileOutputStream(String.valueOf(context.getFilesDir()+pathImage+"/"+idPicture+".jpg"));
            bm2.compress(Bitmap.CompressFormat.JPEG, 50, stream);
            stream.close();
            in.close();

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

Answer 9

使用此类压缩图像

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.net.Uri
import android.os.Environment
import java.io.*


class ImageFile(val uri: Uri, name: String) {

    val filename: String

    init {
        val file = File(Environment.getExternalStorageDirectory().toString() + "/Documents")
        if (!file.exists()) {
            file.mkdirs()
        }
        val fileNoMedia = File(file.absolutePath + "/.nomedia")
        if (!fileNoMedia.exists())
            fileNoMedia.createNewFile()
        if (name.toLowerCase().endsWith(".pdf")) {
            filename = file.absolutePath + "/" + System.currentTimeMillis() + ".pdf"
        } else {
            filename = file.absolutePath + "/" + System.currentTimeMillis() + ".jpg"
        }
    }

    @Throws(IOException::class)
    fun copyFileStream(context: Context, uri: Uri): String {
        if (filename.endsWith(".pdf") || filename.endsWith(".PDF")) {
            var ins: InputStream? = null
            var os: OutputStream? = null
            try {
                ins = context.getContentResolver().openInputStream(uri)
                os = FileOutputStream(filename)
                val buffer = ByteArray(1024)
                var length: Int = ins.read(buffer)
                while (length > 0) {
                    os.write(buffer, 0, length);
                    length = ins.read(buffer)
                }
            } catch (e: Exception) {
                e.printStackTrace();
            } finally {
                ins?.close()
                os?.close()
            }
        } else {
            var ins: InputStream? = null
            var os: OutputStream? = null
            try {
                ins = context.getContentResolver().openInputStream(uri)
                var scaledBitmap: Bitmap? = null
                val options = BitmapFactory.Options()
                options.inJustDecodeBounds = true
                var bmp = BitmapFactory.decodeStream(ins, null, options)
                var actualHeight = options.outHeight
                var actualWidth = options.outWidth

                //      max Height and width values of the compressed image is taken as 816x612
                val maxHeight = 816.0f
                val maxWidth = 612.0f
                var imgRatio = (actualWidth / actualHeight).toFloat()
                val 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 = (imgRatio * actualWidth).toInt()
                        actualHeight = maxHeight.toInt()
                    } else if (imgRatio > maxRatio) {
                        imgRatio = maxWidth / actualWidth
                        actualHeight = (imgRatio * actualHeight).toInt()
                        actualWidth = maxWidth.toInt()
                    } else {
                        actualHeight = maxHeight.toInt()
                        actualWidth = maxWidth.toInt()

                    }
                }

                //      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 = ByteArray(16 * 1024)


                try {
                    //          load the bitmap from its path
                    ins.close()
                    ins = context.getContentResolver().openInputStream(uri)
                    bmp = BitmapFactory.decodeStream(ins, null, options)
                } catch (exception: OutOfMemoryError) {
                    exception.printStackTrace()

                }

                try {
                    scaledBitmap = Bitmap.createBitmap(actualWidth, actualHeight, Bitmap.Config.ARGB_8888)
                } catch (exception: OutOfMemoryError) {
                    exception.printStackTrace()
                }

                val ratioX = actualWidth / options.outWidth.toFloat()
                val ratioY = actualHeight / options.outHeight.toFloat()
                val middleX = actualWidth / 2.0f
                val middleY = actualHeight / 2.0f

                val scaleMatrix = Matrix()
                scaleMatrix.setScale(ratioX, ratioY, middleX, middleY)

                val canvas = Canvas(scaledBitmap!!)
                canvas.matrix = scaleMatrix
                canvas.drawBitmap(bmp, middleX - bmp.width / 2, middleY - bmp.height / 2, Paint(Paint.FILTER_BITMAP_FLAG))

                os = FileOutputStream(filename)
                scaledBitmap.compress(Bitmap.CompressFormat.JPEG, 80, os)
                val buffer = ByteArray(1024)
                var length: Int = ins.read(buffer)
                while (length > 0) {
                    os.write(buffer, 0, length);
                    length = ins.read(buffer)
                }
            } catch (e: Exception) {
                e.printStackTrace();
            } finally {
                ins?.close()
                os?.close()
            }
        }
        return filename
    }

    fun calculateInSampleSize(options: BitmapFactory.Options, reqWidth: Int, reqHeight: Int): Int {
        val height = options.outHeight
        val width = options.outWidth
        var inSampleSize = 1
        if (height > reqHeight || width > reqWidth) {
            val heightRatio = Math.round(height.toFloat() / reqHeight.toFloat())
            val widthRatio = Math.round(width.toFloat() / reqWidth.toFloat())
            inSampleSize = if (heightRatio < widthRatio) heightRatio else widthRatio
        }
        val totalPixels = (width * height).toFloat()
        val totalReqPixelsCap = (reqWidth * reqHeight * 2).toFloat()
        while (totalPixels / (inSampleSize * inSampleSize) > totalReqPixelsCap) {
            inSampleSize++
        }

        return inSampleSize
    }
}

https://lalitjadav007.blogspot.in/2017/08/compress-image-in-android.html

Answer 10

您可以尝试此代码

    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);
        }
    }


    public static String decodeFile(String path,int DESIREDWIDTH, int DESIREDHEIGHT, int type) {
        String strMyImagePath = null;
        Bitmap scaledBitmap = null;
        Bitmap rotated = 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
            scaledBitmap = ScalingUtilities.createScaledBitmap(unscaledBitmap, DESIREDWIDTH, DESIREDHEIGHT, ScalingLogic.FIT);

            String extr = Environment.getExternalStorageDirectory().toString();
            File mFolder = new File(extr + com.vt.vsmart.utils.Config.SD_PATH+"/image");
            if (!mFolder.exists()) {
                mFolder.mkdir();
            }

            String s = type+"temp.jpg";

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

            strMyImagePath = f.getAbsolutePath();
            FileOutputStream fos = null;
            try {
                fos = new FileOutputStream(f);
//                scaledBitmap.compress(Bitmap.CompressFormat.JPEG, 95, fos);

                // quay anh 90 do
                Matrix matrix = new Matrix();

                matrix.postRotate(90);

                rotated = Bitmap.createBitmap(scaledBitmap, 0, 0, scaledBitmap.getWidth(), scaledBitmap.getHeight(), matrix, true);

                rotated.compress(Bitmap.CompressFormat.JPEG, 95, fos);

                fos.flush();
                fos.close();
            } catch (FileNotFoundException e) {

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

                e.printStackTrace();
            }

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

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

    }

    // check anh bi quay
    public int getCameraPhotoOrientation(Context context, Uri imageUri, String imagePath){
        int rotate = 0;
        try {
            context.getContentResolver().notifyChange(imageUri, null);
            File imageFile = new File(imagePath);

            ExifInterface exif = new ExifInterface(imageFile.getAbsolutePath());
            int orientation = exif.getAttributeInt(ExifInterface.TAG_ORIENTATION, ExifInterface.ORIENTATION_NORMAL);

            switch (orientation) {
            case ExifInterface.ORIENTATION_ROTATE_270:
                rotate = 270;
                break;
            case ExifInterface.ORIENTATION_ROTATE_180:
                rotate = 180;
                break;
            case ExifInterface.ORIENTATION_ROTATE_90:
                rotate = 90;
                break;
            }

//            Log.i("RotateImage", "Exif orientation: " + orientation);
//            Log.i("RotateImage", "Rotate value: " + rotate);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return rotate;
    }

}

它对我有用。我希望它可以帮助你！

Answer 11

尝试此方法，这会将您的图像文件转换为压缩格式，并且您可以通过在代码中更改x和y的值来定制压缩级别（在注释行中指示）

      File mImageFile = saveBitmapToFile(ImageFile);

      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=200;        // x............

        // 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 outPutFile = File.createTempFile("abc","image");
        FileOutputStream outputStream = new FileOutputStream(outPutFile);
                                                  // y.......
        selectedBitmap.compress(Bitmap.CompressFormat.JPEG, 95 , outputStream);

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

谢谢

Answer 12

您可以使用this很棒的库进行压缩。在应用程序级别Gradel中添加依赖项：

    dependencies {
    implementation 'id.zelory:compressor:3.0.0'
}

然后像这样压缩实际的图像文件：

val compressedImageFile = Compressor.compress(context, actualImageFile)

Answer 13

您应使用Google的本机图像格式 WebP ，它将shrink the image without losing quality。您可以压缩80％的图片而不会降低质量。

您可以使用CompressFormat.WEBP以WEBP格式编码任何位图。

文件示例：

const int quality = 100; 
FileOutputStream out = new FileOutputStream(path); 
bitmap.compress(Bitmap.CompressFormat.WEBP, quality, out);
out.close();

如何压缩图像大小？

13 个答案: