static int plot_spectrum(const char *filename_png)
{
struct vidframe *vf = NULL;
struct vidsz sz = {NUM_FREQ+1, NUM_FREQ/2};
unsigned long peak_mag = 0;
size_t peak_bin = 0;
size_t i;
unsigned x;
int err;
err = vidframe_alloc(&vf, VID_FMT_RGB32, &sz);
if (err)
goto out;
/* find the peak amplitude and its bin */
for (i=0; i<NUM_FREQ; i++) {
if (magv[i] > peak_mag) {
peak_mag = magv[i];
peak_bin = i;
}
}
re_printf("peak magnitude is %u in bin %u\n", peak_mag, peak_bin);
vidframe_fill(vf, 255, 255, 255);
for (x=0; x<NUM_FREQ; x++) {
unsigned h;
h = (unsigned)((sz.h-1) * 1.0 * magv[x] / peak_mag);
vidframe_draw_vline(vf, x, sz.h-1-h, h, 255, 0, 0);
}
err = png_save_vidframe(vf, filename_png);
if (err)
goto out;
out:
mem_deref(vf);
return err;
}
static inline void clear_frame(struct vidframe *vf)
{
vidframe_fill(vf, 0, 0, 0);
}
