Phosphene is some C code which can be used to plot data in the style of a Cathode Ray Oscilloscope with a green phosphor screen. This may be useful for visualising engineering data in a manner which has a similar aesthetic to the physical hardware.

This code is distribued under an ultra-permissive MIT license with the intention that it may be used within any project with minimal chances of license incompatibilities.

Example usage

scope s;
unsigned int channel = 0; /* channel 0 or 1 */
unsigned int t;
double voltage;
double min_voltage = 0;
double max_voltage = 25;
unsigned int time_step_ms = 1;
unsigned int intensity_percent = 100;
/* dimensions of the oscilloscope grid */
unsigned int grid_horizontal = 10;
unsigned int grid_vertical = 8;
/* image data */
unsigned int img_width = 640;
unsigned int img_height = 480;
unsigned char img[640*480*3];
/* create the oscilloscope */
create_scope(&s, time_step_ms);
s.offset_ms = 0; /* horizontal offset */
s.marker_position = 200; /* position of a marker on the horizontal axis */
s.time_ms = 1000; /* max time on the horizontal axis */
for (t = 0; t < 1000/time_step_ms; t++) {
 /* sinusoidal voltage in the range 0-24v */
 voltage = (1+sin(t*3.1415927/500.0))*max_voltage*0.5;
 scope_update(&s, channel, voltage,
 min_voltage, max_voltage,
 t/time_step_ms, 0);
}
/* create the oscilloscope image */
scope_draw(&s, PHOSPHENE_DRAW_ALL, intensity_percent,
 grid_horizontal, grid_vertical,
 (unsigned char*)img, img_width, img_height,
 PHOSPHENE_SHAPE_RECTANGULAR);
/* save the image to a file */
phosphene_write_png_file("scope1.png",
 (int)img_width, (int)img_height, 24,
 (unsigned char*)img);

Alternatively you can use the scope_draw_graph function to plot with axes and titles.

scope s;
unsigned int channel = 0; /* channel 0 or 1 */
unsigned int t;
double voltage;
double min_voltage = 0;
double max_voltage = 25;
unsigned int time_step_ms = 1;
unsigned int intensity_percent = 100;
/* dimensions of the oscilloscope grid */
unsigned int grid_horizontal = 20;
unsigned int grid_vertical = 16;
/* image data */
unsigned int img_width = 640;
unsigned int img_height = 480;
unsigned char img[640*480*3];
/* create the oscilloscope */
create_scope(&s, time_step_ms);
s.offset_ms = 0; /* horizontal offset */
s.marker_position = 200; /* position of a marker on the horizontal axis */
s.time_ms = 1000; /* max time on the horizontal axis */
for (t = 0; t < 1000/time_step_ms; t++) {
 /* sinusoidal voltage in the range 0-24v */
 voltage = (1+sin(t*3.1415927/500.0))*max_voltage*0.5;
 scope_update(&s, channel, voltage,
 min_voltage, max_voltage,
 t/time_step_ms, 0);
}
/* create the oscilloscope image */
scope_draw_graph(&s, PHOSPHENE_DRAW_ALL, 3, 100,
 grid_horizontal, grid_vertical,
 (unsigned char*)img, img_width, img_height,
 PHOSPHENE_SHAPE_RECTANGULAR,
 "Graph Title",
 "Vertical Values", "Horizontal Values", 15, 4);
/* save the image to a file */
phosphene_write_png_file("scope2.png",
 (int)img_width, (int)img_height, 24,
 (unsigned char*)img);