Generate Thumbnail of Pdf in Android

Using Android PDFRenderer Component

with(context) {
    contentResolver.openFileDescriptor(uri, "r")?.use { parcelFileDescriptor ->
        val pdfRenderer = PdfRenderer(parcelFileDescriptor).openPage(0)
        val bitmap = Bitmap.createBitmap(pdfRenderer.width, pdfRenderer.height, Bitmap.Config.ARGB_8888)
        pdfRenderer.render(bitmap, null, null, PdfRenderer.Page.RENDER_MODE_FOR_DISPLAY)
        pdfRenderer.close()      
    }
}

val file = Constant.allMediaList[position]
val filename = Environment.getExternalStoragePublicDirectory(file)
if (file != null) {
    if (file.endsWith(".pdf")){
        val fd :ParcelFileDescriptor= ParcelFileDescriptor.open(filename,ParcelFileDescriptor.MODE_READ_WRITE)
        val pageNum: Int  = 0;
        val pdfiumCore: PdfiumCore  = PdfiumCore(mContext);
        try {
            val pdfDocument: PdfDocument = pdfiumCore.newDocument(fd);
            pdfiumCore.openPage(pdfDocument, pageNum);
            val width:  Int  = pdfiumCore.getPageWidthPoint(pdfDocument, pageNum);
            val height:  Int = pdfiumCore.getPageHeightPoint(pdfDocument, pageNum);

            // ARGB_8888 - best quality, high memory usage, higher possibility of OutOfMemoryError
            // RGB_565 - little worse quality, twice less memory usage
            val bitmap: Bitmap = Bitmap.createBitmap(width, height,
                  Bitmap.Config.RGB_565);
            pdfiumCore.renderPageBitmap(pdfDocument, bitmap, pageNum, 0, 0,width, height);
            //if you need to render annotations and form fields, you can use
            //the same method above adding 'true' as last param

            Glide.with(mContext)
                .load(bitmap).into(holder.thumbnail)

            pdfiumCore.closeDocument(pdfDocument); // important!
        } catch(ex: IOException) {
            ex.printStackTrace();
            Toast.makeText(mContext,"failed",Toast.LENGTH_LONG).show()
        }

    }

Use PdfiumAndroid as mentioned by barteksc here.

Still working in 2021...

Sample Code for generating Pdf thumb

//PdfiumAndroid (https://github.com/barteksc/PdfiumAndroid)
//https://github.com/barteksc/AndroidPdfViewer/issues/49
void generateImageFromPdf(Uri pdfUri) {
    int pageNumber = 0;
    PdfiumCore pdfiumCore = new PdfiumCore(this);
    try {
        //http://www.programcreek.com/java-api-examples/index.php?api=android.os.ParcelFileDescriptor
        ParcelFileDescriptor fd = getContentResolver().openFileDescriptor(pdfUri, "r");
        PdfDocument pdfDocument = pdfiumCore.newDocument(fd);
        pdfiumCore.openPage(pdfDocument, pageNumber);
        int width = pdfiumCore.getPageWidthPoint(pdfDocument, pageNumber);
        int height = pdfiumCore.getPageHeightPoint(pdfDocument, pageNumber);
        Bitmap bmp = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
        pdfiumCore.renderPageBitmap(pdfDocument, bmp, pageNumber, 0, 0, width, height);
        saveImage(bmp);
        pdfiumCore.closeDocument(pdfDocument); // important!
    } catch(Exception e) {
        //todo with exception
    }
}

public final static String FOLDER = Environment.getExternalStorageDirectory() + "/PDF";
private void saveImage(Bitmap bmp) {
    FileOutputStream out = null;
    try {
        File folder = new File(FOLDER);
        if(!folder.exists())
            folder.mkdirs();
        File file = new File(folder, "PDF.png");
        out = new FileOutputStream(file);
        bmp.compress(Bitmap.CompressFormat.PNG, 100, out); // bmp is your Bitmap instance
    } catch (Exception e) {
        //todo with exception
    } finally {
        try {
            if (out != null)
                out.close();
        } catch (Exception e) {
            //todo with exception
        }
    }
}

---

Update:

Include the library in the build.gradle

implementation 'com.github.barteksc:android-pdf-viewer:3.2.0-beta.1'

For generating Image of any PDF Page:

Call the method generateImageFromPdf(uri) by passing any PDF uri that is stored in your storage.

The method will generate the PDF.png in the PDF folder of your storage.