• 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

• 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

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