Merge pull request #12 from AAnirudh07/main

add image & video reading tutorial

Image Processing/Reading-Image-Video/README.md

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+## Reading-Image-Video
+
+### Reading an image using OpenCV
+- Images can be read using OpenCV's imread() function. 
+
+    **Syntax:** cv2.imread(path, flag)
+
+    **Parameters:**
+    path: A string representing the path of the image to be read.
+    flag: It specifies the way in which image should be read. It’s default value is cv2.IMREAD_COLOR
+
+    **Return Value:** This method returns an image object that is loaded from the specified file.
+
+    For more implementation details, please refer to the associated Python notebook: `read_image_opencv.ipynb`.
+
+### Reading an image using PIL
+- Images can also be read using the Pillow's Image() function.
+    **Syntax:** PIL.Image(path,mode="r")
+
+    **Parameters:**
+    path: A string representing the path of the image to be read.
+    mode – The mode. If given, this argument must be “r”. Hence, this parameter is superfluous.
+
+    **Return Value:** This method returns an image object that is loaded from the specified file.
+
+    For more implementation details, please refer to the associated Python notebook: `read_image_pil.ipynb`.
+
+### Reading videos using OpenCV
+- A video is simply a sequence of frames.
+- OpenCV provides functions for reading video streams as a sequence of frames.
+- OpenCV's video reading methods are widely used.
+
+1. Reading a video using OpenCV
+
+    **Syntax - I:** cv2.VideoCapture(path)
+
+    **Parameters:**
+    path: A string representing the path of the image to be read.
+
+    **Return Value:** This method returns a VideoCapture object that can be used to read the file.
+
+    **Syntax - II:** \<\<VideoCapture object\>\>.read()
+
+    **Parameters:**
+    path: A string representing the path of the image to be read.
+
+    **Return Value:** This method returns two values:
+    1. ret - a flag indicating if the last frame has been read. This value is always false till the last frame.
+    2. frame - frame of a video
+
+    For more implementation details, please refer to the associated Python script: `read_video_opencv.py`.
+
+2. Reading webcam stream using OpenCV
+- Reading a webcam stream is almost the same as reading a video.
+- First, the path attribute in the VideoCapture() function has to be set to 0 to refer to the default computer webcam.
+- Second, the ret value in the read() function does not matter. The stream is stopped as and when the user wishes to.
+
+
+### BONUS: Speed up frame processing using multi-threading
+- Despite its evident advantages, OpenCV is often very slow when it comes to reading video streams. This is because OpenCV reads a video frame-by-frame.
+- The frame rate can be increased by performing the read() method in a separate thread. The main execution thread can then be use the frames generated by the other thread.
+- A popular open-source library, imutils, uses this concept to speed up frame reading. Please refer to the associated python script for more details. (`read_video_imutils.py`)

Image Processing/Reading-Image-Video/read_image_pil.ipynb

@@ -0,0 +1,158 @@
+{
+  "nbformat": 4,
+  "nbformat_minor": 0,
+  "metadata": {
+    "colab": {
+      "provenance": []
+    },
+    "kernelspec": {
+      "name": "python3",
+      "display_name": "Python 3"
+    },
+    "language_info": {
+      "name": "python"
+    }
+  },
+  "cells": [
+    {
+      "cell_type": "markdown",
+      "source": [
+        "### This python notebook shows how to read images using PIL's Image() function. \n",
+        "Image() supports various file formats including, but not limited to, .bmp, .webp, .jpg, .jpeg, and .png."
+      ],
+      "metadata": {
+        "id": "QvWIh7h0hurM"
+      }
+    },
+    {
+      "cell_type": "code",
+      "execution_count": 3,
+      "metadata": {
+        "id": "992nZ6S0hk66"
+      },
+      "outputs": [],
+      "source": [
+        "#Import the necessary libraries\n",
+        "import os\n",
+        "from google.colab import drive\n",
+        "from google.colab.patches import cv2_imshow #used to display images on colab\n",
+        "from PIL import Image"
+      ]
+    },
+    {
+      "cell_type": "code",
+      "source": [
+        "#Connect to Google Drive\n",
+        "drive.mount('/content/drive',force_remount=True)\n",
+        "os.chdir('/content/drive/My Drive')\n",
+        "print(\"Change successful.\")"
+      ],
+      "metadata": {
+        "colab": {
+          "base_uri": "https://localhost:8080/"
+        },
+        "id": "3gS6Rx6ch6n7",
+        "outputId": "45854639-8687-4771-f834-7c7b43990f64"
+      },
+      "execution_count": 2,
+      "outputs": [
+        {
+          "output_type": "stream",
+          "name": "stdout",
+          "text": [
+            "Mounted at /content/drive\n",
+            "Change successful.\n"
+          ]
+        }
+      ]
+    },
+    {
+      "cell_type": "markdown",
+      "source": [
+        "#### Reading an image using Image() [Image(path)]"
+      ],
+      "metadata": {
+        "id": "3-doVYQ4h80E"
+      }
+    },
+    {
+      "cell_type": "code",
+      "source": [
+        "img = Image.open(\"python_logo.png\")\n",
+        "img #this work-around is only for Google Colab. On your local machines please use img.show() to display the image."
+      ],
+      "metadata": {
+        "colab": {
+          "base_uri": "https://localhost:8080/",
+          "height": 242
+        },
+        "id": "Jw5KsuFWiJeT",
+        "outputId": "fe1e289b-a5d0-4900-8e41-b4c1e55eed5b"
+      },
+      "execution_count": 5,
+      "outputs": [
+        {
+          "output_type": "execute_result",
+          "data": {
+            "text/plain": [
+              "<PIL.PngImagePlugin.PngImageFile image mode=P size=225x225 at 0x7FEAD36C64D0>"
+            ],
+            "image/png": "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\n"
+          },
+          "metadata": {},
+          "execution_count": 5
+        }
+      ]
+    },
+    {
+      "cell_type": "markdown",
+      "source": [
+        "#### PIL Image() mode attribute\n",
+        "The mode attribute of the image tells the type and depth of the pixel in the image. A 1-bit pixel has a range of 0-1, and an 8-bit pixel has a range of 0-255. There are different modes provided by this module:\n",
+        "\n",
+        "1  ==> 1-bit pixels, black and white\n",
+        "\n",
+        "L  ==> 8-bit pixels, Greyscale\n",
+        "\n",
+        "P  ==> 8-bit pixels, mapped to any other mode using a color palette\n",
+        "\n",
+        "RGB  ==> 3×8-bit pixels, true color\n",
+        "\n",
+        "RGBA  ==> 4×8-bit pixels, true color with transparency mask"
+      ],
+      "metadata": {
+        "id": "nzsrfm_alTTU"
+      }
+    },
+    {
+      "cell_type": "code",
+      "source": [
+        "img.mode"
+      ],
+      "metadata": {
+        "colab": {
+          "base_uri": "https://localhost:8080/",
+          "height": 36
+        },
+        "id": "270Dia4njPlJ",
+        "outputId": "92bd14a7-82d4-4730-af51-e465749c6175"
+      },
+      "execution_count": 6,
+      "outputs": [
+        {
+          "output_type": "execute_result",
+          "data": {
+            "text/plain": [
+              "'P'"
+            ],
+            "application/vnd.google.colaboratory.intrinsic+json": {
+              "type": "string"
+            }
+          },
+          "metadata": {},
+          "execution_count": 6
+        }
+      ]
+    }
+  ]
+}

Image Processing/Reading-Image-Video/read_video_imutils.py

@@ -0,0 +1,23 @@
+#This Python script shows how to use the imutils library to speed up frame reading
+
+#Import the necessary libraries
+import cv2
+import time
+from imutils.video import WebcamVideoStream
+
+
+#Initialize the WebcamVideoStream object; src=0 refers to the webcam
+vs = WebcamVideoStream(src=0).start()
+
+while True:
+    imutils_frame= vs.read()
+
+    cv2.imshow("IMUTILS",imutils_frame)
+    key = cv2.waitKey(1) 
+    if key == 27: #esc key stops the process
+        break
+
+
+## When everything done, release the object and close all opened windows
+vs.stop()    
+cv2.destroyAllWindows()    

Image Processing/Reading-Image-Video/read_video_opencv.py

@@ -0,0 +1,27 @@
+#This Python script shows how to read a video using OpenCV
+
+#Import the necessary libraries
+import cv2
+
+#Initialize the VideoCapture object
+cap = cv2.VideoCapture('assets/video.mp4')
+
+# Check if camera opened successfully
+if (cap.isOpened()== False):
+  print("Error opening video")
+
+while cap.isOpened():
+    ret, frame = cap.read()
+    if ret:
+        # Display the resulting frame
+        cv2.imshow('Video',frame)
+        # Press Q on keyboard to exit (or) move to the next frame after 1 milliseconds
+        if cv2.waitKey(1) & 0xFF == ord('q'):
+            break
+    else:
+        break
+
+# When everything done, release the video capture object and close all opened windows
+cap.release()
+cv2.destroyAllWindows()
+

Image Processing/Reading-Image-Video/read_webcam_opencv.py

@@ -0,0 +1,22 @@
+#This Python script shows how to read a video using OpenCV
+
+#Import the necessary libraries
+import cv2
+
+#Initialize the VideoCapture object
+cap = cv2.VideoCapture(0)
+
+# Check if camera opened successfully
+if (cap.isOpened()== False):
+  print("Error opening video")
+
+while True:
+    _, frame = cap.read()
+    cv2.imshow('Video',frame)
+    if cv2.waitKey(1) & 0xFF == ord('q'):
+        break
+
+# When everything done, release the video capture object and close all opened windows
+cap.release()
+cv2.destroyAllWindows()
+