- OpenCV - GUI
- OpenCV - Writing an Image
- OpenCV - Reading Images
- OpenCV - Storing Images
- OpenCV - Environment
- OpenCV - Overview
- OpenCV - Home
Types of Images
Image Conversion
Drawing Functions
- OpenCV - Adding Text
- OpenCV - Drawing Arrowed Lines
- OpenCV - Drawing Convex Polylines
- OpenCV - Drawing Polylines
- OpenCV - Drawing an Ellipse
- OpenCV - Drawing a Rectangle
- OpenCV - Drawing a Line
- OpenCV - Drawing a Circle
Blur
Filtering
- OpenCV - Image Pyramids
- OpenCV - Morphological Operations
- OpenCV - Erosion
- OpenCV - Dilation
- OpenCV - Filter2D
- OpenCV - SQRBox Filter
- OpenCV - Box Filter
- OpenCV - Bilateral Filter
Thresholding
Sobel Derivatives
Transformation Operations
Camera and Face Detection
Geometric Transformations
Miscellaneous Chapters
OpenCV Useful Resources
Selected Reading
- Who is Who
- Computer Glossary
- HR Interview Questions
- Effective Resume Writing
- Questions and Answers
- UPSC IAS Exams Notes
OpenCV - Color Maps
In OpenCV, you can apply different color maps to an image using the method applyColorMap() of the class Imgproc. Following is the syntax of this method −
applyColorMap(Mat src, Mat dst, int colormap)
It accepts three parameters −
src − An object of the class Mat representing the source (input) image.
dst − An object of the class Mat representing the destination (output) image.
colormap − A variable of integer type representing the type of the color map to be appped.
Example
The following program demonstrates how to apply color map to an image.
import org.opencv.core.Core; import org.opencv.core.Mat; import org.opencv.imgcodecs.Imgcodecs; import org.opencv.imgproc.Imgproc; pubpc class ColorMapTest { pubpc static void main(String args[]) { // Loading the OpenCV core pbrary System.loadLibrary(Core.NATIVE_LIBRARY_NAME); // Reading the Image from the file and storing it in to a Matrix object String file ="E:/OpenCV/chap25/color_input.jpg"; Mat src = Imgcodecs.imread(file); // Creating an empty matrix to store the result Mat dst = new Mat(); // Applying color map to an image Imgproc.applyColorMap(src, dst, Imgproc.COLORMAP_HOT); // Writing the image Imgcodecs.imwrite("E:/OpenCV/chap25/colormap_hot.jpg", dst); System.out.println("Image processed"); } }
Assume that following is the input image color_input.jpg specified in the above program.
![Color Input](/opencv/images/color_input.jpg)
Output
On executing the above program, you will get the following output −
Image Processed
If you open the specified path, you can observe the output image as follows −
![Color Output](/opencv/images/color_output.jpg)
More Operations
In addition to COLORMAP_HOT demonstrated in the previous example, OpenCV caters various other types of color maps. All these types are represented by predefined static fields (fixed values) of Imgproc class.
You can choose the type of the colormap you need, by passing its respective predefined value to the parameter named colormap of the applyColorMap() method.
Imgproc.applyColorMap(src, dst, Imgproc.COLORMAP_HOT);
Following are the values representing various types of color maps and their respective outputs.
Operation and Description | Output |
---|---|
COLORMAP_AUTUMN | ![]() |
COLORMAP_BONE | ![]() |
COLORMAP_COOL | ![]() |
COLORMAP_HOT | ![]() |
COLORMAP_HSV | ![]() |
COLORMAP_JET | ![]() |
COLORMAP_OCEAN | ![]() |
COLORMAP_PARULA | ![]() |
COLORMAP_PINK | ![]() |
COLORMAP_RAINBOW | ![]() |
COLORMAP_SPRING | ![]() |
COLORMAP_SUMMER | ![]() |
COLORMAP_WINTER | ![]() |