Given an image in PGM format and the task is to invert the image color (making negative) content in PGM format.
PGM image represents a gray scale graphic image. PGM is the abbreviation of Portable Gray Map. This image file contains one or more PGM images file.
Significance of data chunks: The data which are used to create PGM image listed below:
- P2 is the type of image that is grey image
- 4 4 is the image dimension
- 255 is the maximum grey level
- Since, the image data are stored in matrix format and each row indicates the image row and the value indicates the grey level of corresponding pixel. The maximum value (255) is used for white and minimum value (0) is used for black.
P2 4 4 255 255 0 255 0 0 255 0 255 100 200 150 100 50 150 200 0
The input image looks like:
How to invert the image data?
Invert the grey image means change the grey level of an image using (255 – grey lavel) i.e. if grey level of a pixel is 150 then grey level in negative image is (255 – 150) = 105. It means 255 will changes with 0 and 0 will change with 255. It is changing of proportion of black and white present in grey.
P2 4 4 255 0 255 0 255 255 0 255 0 155 55 105 155 205 105 55 255
The output image looks like:
Negative (Invert) Image
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