Grabit is a tool used to grab projects needed to work on. This will assist you in grabbing most projects we work on throughout the course. Just type in Grabit then place project name in the proper directory for the project.

For example: In your gtf0 directory you would type 'grabit UNIX gtf0'

A public directory is need to be able to view your images from a browser

• Create a public html directory with the following command

mkdir -p ~/public_html

• Allow public permissions on the directory with the following

chmod 0711 ~/public_html

• While in your gtf0 directory use the make command to build the code

make gtf0

It is also possible to compile manually

gcc -Wall --std=gnu18 -o gtf0 gtf0.c -lgd

However, it is not necessary to compile GTF0 for Unix due to the shebang added in the first line:

#!/usr/bin/env -S tcc -run -lgd

As such, you are able to run the file as a C script instead of having to compile the program. Simply run with the command:

./gtf0.c

If you were to remove this however, you would need to compile the program before running. An easy way to make sure this shebang is at the top of your file is with the following:

head -n 1 gtf0.c

This is to be runned in the directory that your gtf0.c is in.

Simply enter the command ./gtf0.c inside the gtf0 directory and the program will produce one gtf0.png

• Using the mv command, move the resulting image from your gtf0 dir to your public html dir

mv gtf0.png ~/public_html

• To allow public viewing of the image use the chmod command

chmod 0644 ~/public_html/gtf0.png

• Finally to see the image go to https://lab46.g7n.org/~USER/gtf0.png
• Replacing USER with your username

LibGD is a open source code library that allows images to be created with intuitive functionality

To learn more about LibGD you can visit the LibGD homepage and the LibGD documentation.

Below you will find an assortment of function prototypes that will be useful for completing project GTF0. All of these prototypes have been taken from the LibGD documentation as linked above. These specify function names, parameters and their types, and return values.

Before anything can be drawn there needs to be a color to draw it in

Colors can be mixed with gdImageColorAllocate

int color = gdImageColorAllocate (gdImagePtr im, int r, int g, int b);

gdImagePtr im is the image the function edits

int r, int g, and int b are the red, green, and blue components of the color. Typically represented as hex values between 0x00 and 0xFF

There are many ways to find a colors hex value, including googles

Official gdImageColorAllocate wiki page

gdImageLine (gdImagePtr im, int x1, int y1, int x2, int y2, int color);

gdImagePtr im is the image the function edits

int x1 is the starting x position of the line

int y1 is the starting y position of the line

int x2 is the ending x position of the line

int y2 is the ending y position of the line

int color is the color the line is drawn as

Official gdImageLine wiki page

gdImageRectangle (gdImagePtr im, int x1, int y1, int x2, int y2, int color);

gdImagePtr im is the image the function edits

int x1 is the left bound

int y1 is the upper bound

int x2 is the right bound

int y2 is the lower bound

int color is the color the rectangle is drawn as

Official gdImageRectangle wiki page

gdImageFill (gdImagePtr im, int x, int y, int color);

gdImagePtr im is the image the function edits

int x and int y are the coordinates the fill propagates from

int color is the color that is drawn as

Official gdImageFill wiki page

gdImageFilledRectangle (gdImagePtr im, int x1, int y1, int x2, int y2, int color);

gdImagePtr im is the image the function edits

int x1 is the left bound; i.e., the x coordinate for the top left point of the rectangle to be drawn.

int y1 is the upper bound; similarly, this is the corresponding y coordinate for the top left point of the rectangle.

int x2 is the right bound; this will be the x coordinate of the bottom right point of the rectangle, which incidentally will determine height and width of the rectangle.

int y2 is the lower bound

int color is the color the rectangle is drawn as

Official gdImageFilledRectangle wiki page

gdImageEllipse (gdImagePtr im, int mx, int my, int w, int h, int color);

gdImagePtr im is the image the function edits

int mx and int my is the coordinates of the circle center

int w is the horizontal diameter of the circle

int h is the vertical diameter of the circle

w and h must be the same to create a circle

int color is the color the circle is drawn as

Official gdImageEllipse wiki page

gdImageEllipse (gdImagePtr im, int mx, int my, int w, int h, int color);

gdImagePtr im is the image the function edits

int mx and int my are the coordinates of the ellipse center

int w is the horizontal diameter of the ellipse

int h is the vertical diameter of the ellipse

int color is the color the ellipse is drawn as

Official gdImageEllipse wiki page