example-image-cairo.c

This is a simple example of how to connect to a ScripTouch device and output a PNG image using the Cairo drawing library.

#include <stdio.h>
#include "scriptel-proscript.h"
#include "cairo.h"
 
scriptel_hid_feature_coordinate_range range;
 
cairo_surface_t* surface;
cairo_t* cr;
 
unsigned char penDown = 0;
 
void input_callback(scriptel_device* device, scriptel_input_report* report, unsigned char report_id) {
    if(report_id == SCRIPTEL_INPUT_EXTENDEDCOORDINATE) {
        //We got pen input, lets adjust the coordinates into screen aspect.
        double x = device->display_info.width * ((report->extended_coordinate.x - range.x_min) / (double)(range.x_max - range.x_min));
        double y = device->display_info.height * ((report->extended_coordinate.y - range.y_min) / (double)(range.y_max - range.y_min));
 
        printf("Got a coordinate from the device: %4.2f, %4.2f\n", x, y);
 
        if(report->extended_coordinate.sample_info.pen.tip_switch && !penDown) {
            //Pen Down
            cairo_move_to(cr, x, y);
            penDown = 1;
        } else {
            //Pen Move / Pen Up
            cairo_line_to(cr, x, y);
            penDown = report->extended_coordinate.sample_info.pen.tip_switch;
            if(!penDown) {
                cairo_stroke(cr);
            }
        }
    } else if(report_id == SCRIPTEL_INPUT_BUTTONPRESS) {
        //A button was pressed, if it's the OK button we'll close the device.
        char* caption = report->button_press.region->button.caption;
        printf("Button pressed: %s\n", caption);
        if(strcmp(caption, "OK") == 0) {
            cairo_surface_write_to_png(surface, "signature_cairo.png");
            //The OK button was hit, close the device.
            scriptel_close_device(device);
        } else {
            //The cancel button was hit, clear the image.
            cairo_set_source_rgba (cr, 0xFF, 0xFF, 0xFF, 0);
            cairo_set_operator (cr, CAIRO_OPERATOR_SOURCE);
            cairo_paint (cr);
            cairo_set_operator (cr, CAIRO_OPERATOR_OVER);
            cairo_set_source_rgba (cr, 0, 0, 0, 0xFF);
        }
    }
}
 
int main() {
    scriptel_device* device;
 
    //Initialize the library.
    scriptel_init();
 
    //List the devices.
    if(scriptel_list_devices(&device) == SCRIPTEL_CODE_SUCCESS) {
        //Test to see if we have more than zero devices.
        if(device != NULL) {
            printf("Found %i devices.\n", scriptel_count_device_list(device));
 
            //Lets open the first device and get some information from it.
            if(scriptel_open_device(device) == SCRIPTEL_CODE_SUCCESS) {
                printf("Successfully connected to %s - %s at: %s\n", device->manufacturer, device->model, device->path);
                
                //Register an input callback, this will be called when we get input from the pad.
                scriptel_register_input_callback(device, input_callback);
 
                //Get the coordinate scaling information we'll need later.
                range = scriptel_get_coordinate_range(device);
 
                //Start up Cairo
                surface = cairo_image_surface_create(CAIRO_FORMAT_ARGB32, device->display_info.width, device->display_info.height);
                cr = cairo_create(surface);
                cairo_set_line_width(cr, 1);
 
                //Clear Image with Transparent
                cairo_set_source_rgba (cr, 0xFF, 0xFF, 0xFF, 0);
                cairo_set_operator (cr, CAIRO_OPERATOR_SOURCE);
                cairo_paint (cr);
                cairo_set_operator (cr, CAIRO_OPERATOR_OVER);
                cairo_set_source_rgba (cr, 0, 0, 0, 0xFF);
 
                //Wait for input from the pad.
                while(device->open) {
                    scriptel_device_read(device);
                }
 
                cairo_surface_destroy(surface);
 
                scriptel_free_device_list(device);
            } else {
                printf("Problem opening device: %s\n", scriptel_get_last_error());
                return 1;
            }
        } else {
            printf("No devices found!\n");
            return 2;
        }
    } else {
        printf("Problem enumerating devices: %s\n", scriptel_get_last_error());
        return 3;
    }
}