I\'m using muPDF for reading PDFs in my application. I don\'t like its default animation (Switching horizontally). In other side i found this brilliant library for curl effe
If the muPDF does not support rendering to a bitmap, you have no other choice than rendering to a regular view and take a screen dump to a bitmap like this:
View content = findViewById(R.id.yourPdfView);
Bitmap bitmap = content.getDrawingCache();
Then use this bitmap as input to your other library.
Where should i get pages one by one and converting them to bitmaps?
In our application (newspaper app) we use MuPDF to render PDFs. The workflow goes like this:
So, finally, what we use is MuPDFCore.java and its methods drawPage(...) and onDestroy()
Is this what you want to know or do i miss the point?
EDIT
1.) I think it is not necessary to post code how to download a file. But after downloading i add a RenderTask (extends from Runnable) to a Renderqueue and trigger that queue. The RenderTask needs some information for rendering:
/**
 * constructs a new RenderTask instance
 * @param context: you need Context for MuPdfCore instance
 * @param pageNumber
 * @param pathToPdf 
 * @param renderCallback: callback to set bitmap to the view after    
 * rendering
 * @param heightOfRenderedBitmap: this is the target height
 * @param widthOfRenderedBitmap: this is the target width
 */
public RenderTask (Context context, Integer pageNumber, String pathToPdf, IRenderCallback,    
                   renderCallback, int heightOfRenderedBitmap, 
                   int widthOfRenderedBitmap) {
    //store things in fields
}
2.) + 3.) The Renderqueue wraps the RenderTask in a new Thread and starts it. So the run-method of the RenderTask will be invoked:
@Override
public void run () {
    //do not render it if file exists
    if (exists () == true) {
        finish();
        return;
    }
    Bitmap bitmap = render();
    //if something went wrong, we can't store the bitmap
    if (bitmap == null) {
        finish();
        return;
    }
    //now save the bitmap
    // in my case i save the destination path in a String field
    imagePath = save(bitmap, new File("path/to/your/destination/folder/" + pageNumber + ".jpg"));
    bitmap.recycle();
    finish();
}
/**
 * let's trigger the callback
 */
private void finish () {
    if (renderCallback != null) {
        // i send the whole Rendertask to callback
        // maybe in your case it is enough to send the pageNumber or path to    
        // renderend bitmap   
        renderCallback.finished(this); 
    }
}
/**
 * renders a bitmap
 * @return
 */
private Bitmap render() {
    MuPDFCore core = null;
    try {
        core = new MuPDFCore(context, pathToPdf);
    } catch (Exception e) {
        return null;
    }
    Bitmap bm = Bitmap.createBitmap(widthOfRenderedBitmap, heightOfRenderedBitmap, Config.ARGB_8888);
    // here you render the WHOLE pdf cause patch-x/-y == 0
    core.drawPage(bm, 0, widthOfRenderedBitmap, heightOfRenderedBitmap, 0, 0, widthOfRenderedBitmap, heightOfRenderedBitmap, core.new Cookie());
    core.onDestroy();
    core = null;
    return bm;
}
/**
 * saves bitmap to filesystem
 * @param bitmap
 * @param image
 * @return
 */
private String save(Bitmap bitmap, File image) {
    FileOutputStream out = null;
    try {
        out = new FileOutputStream(image.getAbsolutePath());
        bitmap.compress(Bitmap.CompressFormat.JPEG, 80, out);
        return image.getAbsolutePath();
    } catch (Exception e) {
        return null;
    }
    finally {
        try {
            if (out != null) {
                out.close();
            }
        } catch(Throwable ignore) {}
    }
}  
}
4.) I think it is not necessary to post code how to set a bitmap as background of a view