GIMP Image Editor

GIMP Image Editor:     How to edit images into PGM ?

• GIMP: GNU Image Manipulation Program.
• GIMP Image Editor is a Free and Open Source Image Editor. click here to download and install.
• It is used for converting images into a PGM Extension.

        Different Type of Image Extension:  

             JPEG ->  Joint Photographic Experts Group
             PNG ->   Portable Network Graphics
            XCF ->   eXperimental Computing Facility
             PGM ->  Portable Gray Map

PGM: Portable Gray Map:   

-> In image processing technique, we have to take input as an image. So, the most efficient extension for input image is the ".PGM" extension image.  

-> The ".pgm" extensible Images are editable in a text editor. 

-> The ".xcf, .png, .jpeg" extensible images are not editable in a text editor.

-> ASCII: American Standard Code for Information Interchange.  

 

Process of Converting Images into a PGM Image:

->  Download the GIMP File -> Install.

-> Download image  ->  Save Download Image  ->  "Right Click" on saving image  ->  go to "Open with" and  ->  click on "GIMP Image Editor"  ->  Go to the "file" in open image ->  Click on "save as..."  ->  Go to top and Change the Name: of the file extension into "pgm"  ->  Go to right bottom corner, click "Save"  ->  Click "Take me to the Export dialog"  ->  Go to Right bottom corner and click "Export"  ->  Choose "ASCII"  ->  Export.

Image Processing using C-Programming

Image: 

• An image is a two-dimensional (2-D) array of pixels.
• There are mainly two types of Image.

1. R-G-B Channel Image: The R-G-B Images are formed by three primary channel called a color image. Red, Green and Blue are three channels in a color image.
   
2. Single Channel Image: Monochrome Image that has pixel's intensity ranging from 0 to 255 is called Single Channel Image. 

Example:

Figure 1. A Monochrome Image

Image Contrast Stretching using C-Programming.

Contrast Stretching in Image Processing:

• It is an image processing technique for low-contrast images.
• The low-contrast images can result from poor illumination and wrong setting of a lens aperture during image acquisition.
• Contrast stretching is a process that expands the range of intensity levels in an image.

#include<stdio.h>

#include<stdlib.h>

#include<math.h>

void main()

{

int i,j,row,col,max,pix,v=0,max1=0,min=1000;

char c[10],a[100];

FILE *p,*q;

p=fopen("cot.pgm","r");

fscanf(p,"%s\n", c);

fscanf(p,"%[^\n]\n", a);

fscanf(p,"%d %d\n", &col ,&row);

fscanf(p,"%d\n",&max);

int m[row][col],m1[row][col],m2[256];

for(i=0;i<row;i++)

{

for(j=0;j<col;j++)

{

fscanf(p,"%d\n",&pix);

m[i][j]=pix;

if(max1<pix)

max1=pix;

if(min>pix)

min=pix;

}

}printf("%d %d\n", max1,min);

for(i=0;i<row;i++)

{

for(j=0;j<col;j++)

{

m[i][j]=((255*(m[i][j]-min)/(max1-min)));

}

}

q=fopen("d31.pgm","w");

fprintf(q,"%s\n",c);

fprintf(q,"%s\n",a);

fprintf(q,"%d %d\n", col, row);

fprintf(q,"%d\n",max);

for(i=0;i<row;i++)

{

for(j=0;j<col;j++)

{

pix=m[i][j];

fprintf(q,"%d\n",pix);

}

}

fclose(p);

fclose(q);

} 

Generic Pointer in C

Void Pointer or Generic Pointer (void *) in C

Pointers: 

-> A pointer is a derived data type in C-Programming.

-> It builds from one of the fundamental data types (int, float, char, and double).

-> The declaration of a pointer variable is as follows: data_type *pointer_name

Example 1:      int *P;

                         float *x;

-> Ampersand Symbol ( & ) in C-Programming represents the "address of" operator.    

Example 2:      int quantity;

                        int *P; 

                        P = &quantity;     

-> In this syntax, integer, pointer variable 'P' store the address of an integer variable quantity. 

Example 3:        float rate;

                           int *P;

                           P = &rate

-> The syntax given in Example 3 is wrong. Since, Compatibility and Casting problems.

-> Therefore, we cannot assign the address of floating variable rate into the integer pointer variable P.

-> The problem of Compatibility and Casting, can be solved by using Generic Pointer.

The Generic Pointer:

-> The void pointer is a generic pointer that can represent any pointer type.

-> All pointer types can be assigned to a void pointer and a void pointer can be assigned to any pointer without casting. 

Example 4:            void *vp;    (generic pointer)

                               float rate;

                               vp = &rate;

-> A pointer variable 'vp' with type void is called generic pointer.

-> The syntax in Example 4, resolve the problem of Compatibility and Casting and void pointer vp store the address of floating point variable rate.

Q.1. Why we use a generic pointer in C-Programming ?

Complexity of Infinite Loop

Infinite Loop in C                           

"Infinite Loop in C-code means the loop does not terminate."

C-Compiler: Code Blocks (https://sourceforge.net/projects/codeblocks/), Turbo C++, Dev-C++ (https://sourceforge.net/software/product/Embarcadero-Dev-Cpp/)

Example 1.

C-programing in Linux platform:

1. Open a text-editor -> Write C-code -> Press (ctrl+shift+s) -> type filename.c -> Click on save .

2. Open command prompt (a) For compilation: Type gcc filename.c (b) For execution: Type ./a.out

There are mainly four types of infinite loop in C-programming.

(i) By calling the main function into the main().

(ii) By using for-loop.

(iii) By using while-loop.

(iv) By using do-while-loop.   

# include<stdio.h>

void main ()

{

printf ("hello");

main();

}

The output of this C-programming: hellohellohello--------------till interrupt (ctrl+z). 

#include<stdio.h>

int main()

{

for(;;)

{

printf("hello \n");

}

return(0);

}

#include<stdio.h>

int main()

{

while(1)

{

printf("hello\n");

}

return(0);

}

#include<stdio.h>

int main()

{

do

{

printf("hello\n");

}

while(1);

return(0);

}

If the return type of main() function is an integer then we must include a return(0) function in our code.  

On Windows Platforms (Turbo C++):

Example 2.

#include<stdio.h>

#include<conio.h>

void main ()

{

for (;;)

{

printf ("hello");

}

clrscr ();

getch ();

}

In "Turbo c++" compiler, we must include getch() and clrscr() function for displaying the output on clear screen.