如何在上传到服务器之前减小图像文件大小 [英] How to reduce an Image file size before uploading to a server

问题描述

许多应用程序允许共享从图库中挑选的图像.

Lot of application allow sharing an image, which is picked from the gallery.

他们会上传原始图像文件吗?哪个是 1-3 mb?还是他们处理?

Do they upload the original image file? Which is like 1-3 mb? Or do they process?

无论如何，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位置并尝试上传?

In any case, how can I take the image from a filepath, reduce its size by lowering the resolution and save it some where else and the try to upload?

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);
}

但这是他们正确的做法吗?因为我看到的答案表明压缩操作需要相当多的时间 here

But is this they right way to do? Because I have seen answers suggesting compression operation takes rather big amount of time here

推荐答案

我用这个功能在上传图片之前缩小图片大小，将图片缩小到近200 KB，并保持质量相对较好，你可以修改它通过更改 REQUIRED_SIZE 和 inSampleSize 来实现您的目的:

I use this function to reduce the size of image before uploading it, it reduces the image size to nearly 200 KB and keep the quality relatively good, u may modify it to fulfill your purpose by changing the REQUIRED_SIZE and inSampleSize:

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.

NOTE: I resize and override the original file image in this function, u may write it to another file as well.

希望对你有帮助.

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