Merge pull request #25326 from gursimarsingh:improved_text_detection_sample

Improved and refactored text detection sample in dnn module #25326

Clean up samples: #25006

This pull requests merges and simplifies different text detection samples in dnn module of opencv in to one file. An option has been provided to choose the detection model from EAST or DB

### Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [x] There is a reference to the original bug report and related work
- [ ] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [x] The feature is well documented and sample code can be built with the project CMake

doc/tutorials/dnn/dnn_text_spotting/dnn_text_spotting.markdown

@@ -14,6 +14,7 @@
 In this tutorial, we will introduce the APIs for TextRecognitionModel and TextDetectionModel in detail.
 
 ---
+
 ### TextRecognitionModel
 
 In the current version, @ref cv::dnn::TextRecognitionModel only supports CNN+RNN+CTC based algorithms,
@@ -292,38 +293,13 @@ of these APIs can be found in the DNN module.
 
 ## Detailed Sample
 For more information, please refer to:
-- [samples/dnn/scene_text_recognition.cpp](https://github.com/opencv/opencv/blob/5.x/samples/dnn/scene_text_recognition.cpp)
-- [samples/dnn/scene_text_detection.cpp](https://github.com/opencv/opencv/blob/5.x/samples/dnn/scene_text_detection.cpp)
 - [samples/dnn/text_detection.cpp](https://github.com/opencv/opencv/blob/5.x/samples/dnn/text_detection.cpp)
-- [samples/dnn/scene_text_spotting.cpp](https://github.com/opencv/opencv/blob/5.x/samples/dnn/scene_text_spotting.cpp)
 
 ### Test with an image
+Detection models can be downloaded using:
+- [samples/dnn/download_models.py](https://github.com/opencv/opencv/blob/5.x/samples/dnn/download_models.py)
+All the preprocessing parameters will be loaded from [samples/dnn/models.yml](https://github.com/opencv/opencv/blob/5.x/samples/dnn/models.yml)
 Examples:
 ```bash
-example_dnn_scene_text_recognition -mp=path/to/crnn_cs.onnx -i=path/to/an/image -rgb=1 -vp=/path/to/alphabet_94.txt
-example_dnn_scene_text_detection -mp=path/to/DB_TD500_resnet50.onnx -i=path/to/an/image -ih=736 -iw=736
-example_dnn_scene_text_spotting -dmp=path/to/DB_IC15_resnet50.onnx -rmp=path/to/crnn_cs.onnx -i=path/to/an/image -iw=1280 -ih=736 -rgb=1 -vp=/path/to/alphabet_94.txt
-example_dnn_text_detection -dmp=path/to/EAST.pb -rmp=path/to/crnn_cs.onnx -i=path/to/an/image -rgb=1 -vp=path/to/alphabet_94.txt
-```
-
-### Test on public datasets
-Text Recognition:
-
-The download link for testing images can be found in the **Images for Testing**
-
-
-Examples:
-```bash
-example_dnn_scene_text_recognition -mp=path/to/crnn.onnx -e=true -edp=path/to/evaluation_data_rec -vp=/path/to/alphabet_36.txt -rgb=0
-example_dnn_scene_text_recognition -mp=path/to/crnn_cs.onnx -e=true -edp=path/to/evaluation_data_rec -vp=/path/to/alphabet_94.txt -rgb=1
-```
-
-Text Detection:
-
-The download links for testing images can be found in the **Images for Testing**
-
-Examples:
-```bash
-example_dnn_scene_text_detection -mp=path/to/DB_TD500_resnet50.onnx -e=true -edp=path/to/evaluation_data_det/TD500 -ih=736 -iw=736
-example_dnn_scene_text_detection -mp=path/to/DB_IC15_resnet50.onnx -e=true -edp=path/to/evaluation_data_det/IC15 -ih=736 -iw=1280
-```
+example_dnn_text_detection DB
+```