If you can, try pre-processing and inverting the image so it is black text
on a white background. I found that recognition works much better with the
preprocessing (probably since the models were trained with that kind of
input)
On Tuesday, July 30, 2024 at 10:45:56 PM UTC+8 allelu...@gmail.com wrote:
> I'm trying to use a tesseract in project wrote in C#. I have a problem
> with reading text from a part of an image. I'm trying to find this 4 signs
> (in example 0000) and number after "e". Additionally, for some examples it
> is working perfectly but for some others its printing "Empty page!!!".
> Difference between examples is color of the background but whole image
> processing is the same for every try. What should I do to minimize
> probability of error?
>
>
> Thats the image where ocr is working correctly:
> [image: working.jpg]
>
> and here is not working:
>
> [image: not working.jpg]
>
>
>
> Part of code in c#:
>
>
> public static class Sign
> {
> public static void Verify()
> {
> string imagePath = "path.bmp";
> Mat imageSign = new Mat(imagePath);
>
> int h = imageSign.Rows;
> int w = imageSign.Cols;
> int point1 = (int)(0.01 * w);
> int point2 = (int)(0.6 * h);
> int point3 = (int)(0.3 * w);
> int point4 = (int)(0.9 * h);
> OpenCvSharp.Point start_point = new OpenCvSharp.Point(point1,
> point2);
> OpenCvSharp.Point end_point = new OpenCvSharp.Point(point3,
> point4);
> imageSign = new Mat(imageSign, new OpenCvSharp.Rect(point1,
> point2, point3 - point1, point4 - point2));
> Cv2.Resize(imageSign, imageSign, new OpenCvSharp.Size(), 2, 2);
> imageSign.SaveImage(imagePath);
>
> using (Bitmap bitmap = (Bitmap)Image.FromFile(imagePathE))
> {
> using (Bitmap newBitmap = new Bitmap(bitmap))
> {
> string imagePathA = "2nd image path.bmp";
> newBitmap.SetResolution(300, 300);
> newBitmap.Save(imagePathA);
> }
> }
>
>
>
>
> string imagePathB = " "2nd image path.bmp " ;
> var pixFromFile = Pix.LoadFromFile(imagePathB);
> string customConfig = "--psm 10 --oem 3";
> using (var engine = new TesseractEngine(@"C:\Program
> Files\Tesseract-OCR\tessdata", "eng", EngineMode.Default))
> {
>
> engined.SetVariable("tessedit_char_whitelist", "0123456789");
> using (var page = engined.Process(pixFromFile, customConfig))
> {
> string text = page.GetText();
> Console.Write(text);
>
> string[] lines = text.Split('\n');
> bool linijka = false;
>
> foreach (string line in lines)
> {
> if (line.Length == 4 || line.Length == 5)
> {
> Console.WriteLine("Oznaczenie e5: ");
> Console.WriteLine(line);
> linijka = true;
> }
> if (line.Length == 1)
> {
> Console.WriteLine("e_:");
> Console.WriteLine(line);
> }
> }
>
>
> Cv2.ImShow("koniec", imageSign);
> Cv2.WaitKey(0);
> }
> }
>
> I tried cropping an image and for some reason when i making it bigger or
> smaller than it is now, it adversely affects on results. Additionally I
> tried some other tesseract psm configurations and changed dpi of image to
> 300.
>
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