int stride;
unsigned char *data;
cairo_surface_t *surface;

stride = cairo_format_stride_for_width (format, width);
data = malloc (stride * height);
surface = cairo_image_surface_create_for_data (data, format,
					  width, height,
					  stride);

cairo_surface_t *
cairo_image_surface_create_for_data (unsigned char *data,
                                     cairo_format_t format,
                                     int width,
                                     int height,
                                     int stride);

CAIRO_FORMAT_RGB24
each pixel is a 32-bit quantity, with the upper 8 bits unused. Red, Green, and Blue are stored in the remaining 24 bits in that order. (Since 1.0)

CAIRO_FORMAT_ARGB32
each pixel is a 32-bit quantity, with alpha in the upper 8 bits, then red, then green, then blue. The 32-bit quantities are stored native-endian. Pre-multiplied alpha is used. (That is, 50% transparent red is 0x80800000, not 0x80ff0000.) (Since 1.0)


unsigned char *     cairo_image_surface_get_data        (cairo_surface_t *surface);
get pointer to imag data for inspection _and_ manipulation




first disable Auto FFC (autoFFC:false)
Code: [Select]

            //--------- write string: {"type":"setOption","data":{"option":"autoFFC","value":false}}
            length = 16;
            unsigned char my_string4[16]={0xcc,0x01,0x00,0x00,0x01,0x00,0x00,0x00,0x3f,0x00,0x00,0x00,0x57,0x64,0x17,0x8b};
            printf("\nEP 0x02 to be sent Hexcode: %i Bytes[",length);
            for (i = 0; i < length; i++) {
                printf(" %02x", my_string4[i]);

            }
            printf(" ]\n");

            r = libusb_bulk_transfer(devh, 2, my_string4, length, &transferred, 0);
            if(r == 0 && transferred == length)
            {
                printf("\nWrite successful!");
            }
            else
                printf("\nError in write! res = %d and transferred = %d\n", r, transferred);

            strcpy(  my_string,"{\"type\":\"setOption\",\"data\":{\"option\":\"autoFFC\",\"value\":false}}");
            length = strlen(my_string)+1;
            printf("\nEP 0x02 to be sent %i Bytes: %s", length, my_string);

            // avoid error: invalid conversion from ‘char*’ to ‘unsigned char*’ [-fpermissive]
            my_string1 = (unsigned char*)my_string;

            r = libusb_bulk_transfer(devh, 2, my_string1, length, &transferred, 0);
            if(r == 0 && transferred == length)
            {
                printf("\nWrite successful!");
                printf("\nSent %d bytes with string: %s\n", transferred, my_string);
            }
            else
                printf("\nError in write! res = %d and transferred = %d\n", r, transferred);


and trigger if required a manual FCC (doFFC:true)
Code: [Select]

                unsigned char my_string2[16]={0xcc,0x01,0x00,0x00,0x01,0x00,0x00,0x00,0x3c,0x00,0x00,0x00,0xb9,0xcb,0xa2,0x99};

                r = libusb_bulk_transfer(devh, 2, my_string2, length, &transferred, 0);
                if(r == 0 && transferred == length)
                    printf("\nWrite successful!");
                else
                    printf("\nError in write! res = %d and transferred = %d\n", r, transferred);

                char my_string[128];
                transferred = 0;

                strcpy(my_string, "{\"type\":\"setOption\",\"data\":{\"option\":\"doFFC\",\"value\":true}}");
                length = strlen(my_string)+1;

                unsigned char *my_string1 = (unsigned char*)my_string;