public static List <PDFPage> GetPDFPages(Stream pdfStream, TraceWriter log, bool ocrImages = false)
{
var result = new List <PDFPage>();
pdfStream.Position = 0; // Ensure that we are at the start
// Note: PdfReader Dispose closes the stream...
using (PdfReader reader = new PdfReader(pdfStream))
{
var numberOfPages = reader.NumberOfPages;
var parser = new PdfReaderContentParser(reader);
ImageRenderListener listener = null; // = new ImageRenderListener(log);
for (var i = 1; i <= reader.NumberOfPages; i++)
{
var page = new PDFPage {
Number = i
};
try
{
parser.ProcessContent(i, (listener = new ImageRenderListener(log)));
}
catch (Exception ex)
{
log.Error(string.Format("Page {0} Image Processing Exception", i), ex);
}
if (listener.Images.Count > 0)
{
log.Info(string.Format("Found {0} images on page {1}.", listener.Images.Count, i));
page.ExtractedImages = listener.Images;
if (ocrImages)
{
if (listener.Images.Count < 10)
{
log.Info("Calling Vision API to OCR Page Images");
VisionAPIHelper.OCRPage(page, log);
}
else
{
log.Info("Too many Page Images for Vision API");
}
}
}
try
{
page.PageText = PdfTextExtractor.GetTextFromPage(reader, i, new SimpleTextExtractionStrategy());
}
catch (System.ArgumentException ex)
{
log.Error(string.Format("Page {0} Text Processing Exception", i), ex);
}
result.Add(page);
}
}
return(result);
}
public static void OCRPage(PDFPage thisPage, TraceWriter log)
{
foreach (var img in thisPage.ExtractedImages)
{
// Image must be Bitmap
if (!(img is Bitmap))
{
log.Info("Found image that was not Bitmap - ignoring");
continue;
}
// Image must be at least 40 x 40
if (img.Width < 40 || img.Height < 40)
{
log.Info("Image is too small - ignoring");
continue;
}
// Convert this image to grayscale (must be Bitmap as we discovered earlier)
var bmp = (Bitmap)img; // In case Grayscale fails - just use it as-is
if (img.PixelFormat != PixelFormat.Format1bppIndexed &&
img.PixelFormat != PixelFormat.Format8bppIndexed)
{
try
{
bmp = Grayscale.CommonAlgorithms.BT709.Apply((Bitmap)img);
}
catch (Exception) { }
}
// Image can't be larger than 3200 x 3200
if (bmp.Width > 3200 || bmp.Height > 3200)
{
log.Info(string.Format("Image is too big {0} x {1} - dealing with that...", bmp.Width, bmp.Height));
if (bmp.Width < 3500 && bmp.Height < 3500)
{
// Lets crop it - hopefully there are margins
log.Info("Cropping the image");
// Calculate Crop Rectangle
var rect = new System.Drawing.Rectangle(0, 0, bmp.Width, bmp.Height);
if (bmp.Width > 3200)
{
var halfWideCrop = (bmp.Width - 3200) / 2;
rect.X = halfWideCrop;
rect.Width = bmp.Width - halfWideCrop;
}
if (bmp.Height > 3200)
{
var halfHighCrop = (bmp.Width - 3200) / 2;
rect.Y = halfHighCrop;
rect.Height = bmp.Height - halfHighCrop;
}
Crop cropFilter = new Crop(rect);
bmp = cropFilter.Apply(bmp);
}
else
{
// Scale the image down
log.Info("Resizing the image");
// Calculate the shrinkage
int newWidth, newHeight;
if (bmp.Width > bmp.Height)
{
var scaleFactor = bmp.Width / 3200F;
newWidth = Convert.ToInt32(bmp.Width / scaleFactor);
newHeight = Convert.ToInt32(bmp.Height / scaleFactor);
}
else
{
var scaleFactor = bmp.Height / 3200F;
newWidth = Convert.ToInt32(bmp.Width / scaleFactor);
newHeight = Convert.ToInt32(bmp.Height / scaleFactor);
}
if (newWidth > 3200 || newHeight > 3200)
{
throw new ApplicationException("DOH! Miscalculated Scale");
}
try
{
ResizeBicubic resizeFilter = new ResizeBicubic(newWidth, newHeight);
bmp = resizeFilter.Apply(bmp);
}
catch (AForge.Imaging.UnsupportedImageFormatException)
{
return;
}
}
}
var ms = new MemoryStream();
bmp.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
ms.Position = 0;
try
{
Task <string> recoTask = Task.Run <string>(async() =>
{
var result = await UploadAndRecognizeImageTextAsync(ms, "en");
return(result);
});
recoTask.Wait();
var ocrResult = recoTask.Result;
thisPage.OCRText += ocrResult.Trim() + "\r\n";
}
catch (Exception ex)
{
log.Warning(string.Format("Page {0} OCR Exception: {1}", thisPage.Number, ex.Message));
}
}
}
