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add grid to inline-spectrum

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This commit is contained in:
Robin Gareus 2016-07-03 14:46:29 +02:00
parent 9220e81e20
commit 913609becc
1 changed files with 45 additions and 7 deletions
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52
scripts/spectrogram.lua
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@ -145,6 +145,7 @@ local read_ptr = 0
local line = 0
local img = nil
local fft_size = 0
local last_log = false
function render_inline (ctx, w, max_h)
local ctrl = CtrlPorts:array () -- get control port array (read/write)
@ -188,6 +189,12 @@ function render_inline (ctx, w, max_h)
fft = ARDOUR.DSP.FFTSpectrum (fft_size, rate)
end
if last_log ~= logscale then
last_log = logscale
img = nil
line = 0
end
-- calc height
if hmode == 0 then
h = math.ceil (w * 10 / 16)
@ -209,13 +216,19 @@ function render_inline (ctx, w, max_h)
if not img or img:get_width() ~= w or img:get_height () ~= h then
img = Cairo.ImageSurface (Cairo.Format.ARGB32, w, h)
end
local ictx = img:context ()
-- read ring-buffer, analyze
local bins = fft_size / 2 - 1 -- fft bin count
local bpx = bins / w -- bins per x-pixel (linear)
local fpb = rate / fft_size -- freq-step per bin
local f_e = rate / 2 / fpb -- log-scale exponent
local f_b = w / math.log (fft_size / 2) -- inverse log-scale base
local f_l = math.log (fft_size / rate) * f_b -- inverse logscale lower-bound
-- available samples in ring-buffer
local write_ptr = shmem:atomic_get_int (0)
local avail = (write_ptr + buf_size - read_ptr) % buf_size
local ictx = img:context ()
while (avail >= fft_size) do
-- process one line / buffer
if read_ptr + fft_size < buf_size then
@ -232,12 +245,8 @@ function render_inline (ctx, w, max_h)
avail = (write_ptr + buf_size - read_ptr ) % buf_size
-- draw spectrum
local bins = fft_size / 2 - 1
local bpx = bins / w
local fpb = rate / fft_size
assert (bpx >= 1)
local f_e = rate / 2 / fpb
-- scroll
if line == 0 then line = h - 1; else line = line - 1; end
@ -292,5 +301,34 @@ function render_inline (ctx, w, max_h)
ctx:fill ()
end
-- draw grid on top
function x_at_freq (f)
if logscale then
return f_l + f_b * math.log (f)
else
return 2 * w * f / rate;
end
end
function grid_freq (f)
-- draw vertical grid line
local x = .5 + math.floor (x_at_freq (f))
ctx:move_to (x, 0)
ctx:line_to (x, h)
ctx:stroke ()
end
-- draw grid on top
local dash3 = C.DoubleVector ()
dash3:add ({1, 3})
ctx:set_line_width (1.0)
ctx:set_dash (dash3, 2) -- dotted line
ctx:set_source_rgba (.5, .5, .5, .8)
grid_freq (100)
grid_freq (1000)
grid_freq (10000)
ctx:unset_dash ()
return {w, h}
end