Re: [NTG-context] colors and contours in luametafun
On 6/20/2022 6:29 PM, Jacob Kauffmann via ntg-context wrote:
Dear list,
Am 01.09.2021 um 09:54 schrieb Jacob Kauffmann via ntg-context
:
- color by value in lmt_surface
We want to show a surface plot of a function where the color indicates the
function value (instead, or in addition to a light source).
The easiest would be to have variable cf for the brightness factor (as it is),
and in addition variables such as zt, minz, maxz, akin to the color formatter
for lmt_contour.
This becomes handy when colors are to be aligned with function values (e.g.
negative = blue, zero = white, positive = red, see MWE attached).
I managed to achieve this by tweaking f_color and mp.lmt_surface_do in
mlib-cnt.lmt in
ConTeXt ver: 2022.05.11 11:36 LMTX fmt: 2022.6.20
a bit.
Please find the diff and a MWE attached.
in next version (next time just send me the file, easier than a diff)
Cheers,
Jacob Kauffmann
--- context/tex/texmf-context/tex/context/base/mkxl/mlib-cnt.lmt 2022-06-20
18:11:51.0 +0200
+++ mlib-cnt.lmt2022-06-20 18:26:22.0 +0200
@@ -1839,7 +1839,29 @@
local f_color = formatters [ [[
local math = math
-return function(f)
+local min = math.min
+local max = math.max
+local abs = math.abs
+local minz = %s
+local maxz = %s
+
+local color_value = 0
+local color_step = mp.lmt_color_functions.step
+local color_shade = mp.lmt_color_functions.shade
+
+local function step(...)
+return color_step(color_value,n,...)
+end
+local function shade(...)
+return color_shade(color_value,n,...)
+end
+-- local function lin(l)
+-- return l/n
+-- end
+%s
+return function(z, f)
+function_value = z
+brightness_factor = f
return %s
end
]] ]
@@ -1898,7 +1920,7 @@
local dy = (ymax - ymin) / ny
local xt = xmin
--
-local minf, maxf
+local minf, maxf, minz, maxz
--
-- similar as contours but no data loop here
--
@@ -1908,12 +1930,6 @@
return false -- fatal error
end
--
-local ccode = load(f_color(colorcode))
-local color = type(ccode) == "function" and ccode()
-if type(color) ~= "function" then
-return false -- fatal error
-end
---
for i=0,nx do
local yt = ymin
for j=0,ny do
@@ -1946,7 +1962,16 @@
maxf = fac
end
--
-data[i][j] = { x, y, fac }
+if not minz then
+ minz = z
+ maxz = z
+elseif z < minz then
+ minz = z
+elseif z > maxz then
+ maxz = z
+end
+--
+data[i][j] = { x, y, fac, z }
--
yt = yt + dy
end
@@ -1957,6 +1982,16 @@
local range = maxf - minf
local cl = linecolor or 1
local enforce = attributes.colors.model == "cmyk"
+--
+-- local ccode = load(f_color(colorcode))
+report("minz, maxz is (%s,%s)",minz,maxz)
+report("colorcode is %s", colorcode)
+local ccode = load(f_color(minz, maxz, preamble, colorcode))
+local color = type(ccode) == "function" and ccode()
+if type(color) ~= "function" then
+return false -- fatal error
+end
+--
for i=0,nx-1 do
for j=0,ny-1 do
-- points
@@ -1985,12 +2020,13 @@
local z32 = z3[2]
local z41 = z4[1]
local z42 = z4[2]
+local zout = z1[4]
-- if lines then
-- -- fill first and draw then, previous shapes can be covered
-- else
-- -- fill and draw in one go to prevent artifacts
-- end
-local cr, cg, cb = color(cf)
+local cr, cg, cb = color(zout, cf)
if not cr then cr = 0 end
if not cg then cg = 0 end
if not cb then cb = 0 end
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Re: [NTG-context] colors and contours in luametafun
Dear list,
> Am 01.09.2021 um 09:54 schrieb Jacob Kauffmann via ntg-context
> :
> - color by value in lmt_surface
> We want to show a surface plot of a function where the color indicates the
> function value (instead, or in addition to a light source).
> The easiest would be to have variable cf for the brightness factor (as it
> is), and in addition variables such as zt, minz, maxz, akin to the color
> formatter for lmt_contour.
> This becomes handy when colors are to be aligned with function values (e.g.
> negative = blue, zero = white, positive = red, see MWE attached).
I managed to achieve this by tweaking f_color and mp.lmt_surface_do in
mlib-cnt.lmt in
ConTeXt ver: 2022.05.11 11:36 LMTX fmt: 2022.6.20
a bit.
Please find the diff and a MWE attached.
Cheers,
Jacob Kauffmann
--- context/tex/texmf-context/tex/context/base/mkxl/mlib-cnt.lmt 2022-06-20
18:11:51.0 +0200
+++ mlib-cnt.lmt2022-06-20 18:26:22.0 +0200
@@ -1839,7 +1839,29 @@
local f_color = formatters [ [[
local math = math
-return function(f)
+local min = math.min
+local max = math.max
+local abs = math.abs
+local minz = %s
+local maxz = %s
+
+local color_value = 0
+local color_step = mp.lmt_color_functions.step
+local color_shade = mp.lmt_color_functions.shade
+
+local function step(...)
+return color_step(color_value,n,...)
+end
+local function shade(...)
+return color_shade(color_value,n,...)
+end
+-- local function lin(l)
+-- return l/n
+-- end
+%s
+return function(z, f)
+function_value = z
+brightness_factor = f
return %s
end
]] ]
@@ -1898,7 +1920,7 @@
local dy = (ymax - ymin) / ny
local xt = xmin
--
-local minf, maxf
+local minf, maxf, minz, maxz
--
-- similar as contours but no data loop here
--
@@ -1908,12 +1930,6 @@
return false -- fatal error
end
--
-local ccode = load(f_color(colorcode))
-local color = type(ccode) == "function" and ccode()
-if type(color) ~= "function" then
-return false -- fatal error
-end
---
for i=0,nx do
local yt = ymin
for j=0,ny do
@@ -1946,7 +1962,16 @@
maxf = fac
end
--
-data[i][j] = { x, y, fac }
+if not minz then
+ minz = z
+ maxz = z
+elseif z < minz then
+ minz = z
+elseif z > maxz then
+ maxz = z
+end
+--
+data[i][j] = { x, y, fac, z }
--
yt = yt + dy
end
@@ -1957,6 +1982,16 @@
local range = maxf - minf
local cl = linecolor or 1
local enforce = attributes.colors.model == "cmyk"
+--
+-- local ccode = load(f_color(colorcode))
+report("minz, maxz is (%s,%s)",minz,maxz)
+report("colorcode is %s", colorcode)
+local ccode = load(f_color(minz, maxz, preamble, colorcode))
+local color = type(ccode) == "function" and ccode()
+if type(color) ~= "function" then
+return false -- fatal error
+end
+--
for i=0,nx-1 do
for j=0,ny-1 do
-- points
@@ -1985,12 +2020,13 @@
local z32 = z3[2]
local z41 = z4[1]
local z42 = z4[2]
+local zout = z1[4]
-- if lines then
-- -- fill first and draw then, previous shapes can be covered
-- else
-- -- fill and draw in one go to prevent artifacts
-- end
-local cr, cg, cb = color(cf)
+local cr, cg, cb = color(zout, cf)
if not cr then cr = 0 end
if not cg then cg = 0 end
if not cb then cb = 0 end
colors_and_surface_in_luametafun.pdf
Description: Adobe PDF document
colors_and_surface_in_luametafun.tex
Description: Binary data
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Description: Message signed with OpenPGP
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[NTG-context] colors and contours in luametafun
Dear list,
I am a huge fan of the new metafun interface.
Hans asked for luametafun requests, so here are a few.
- color by value in lmt_surface
We want to show a surface plot of a function where the color indicates the
function value (instead, or in addition to a light source).
The easiest would be to have variable cf for the brightness factor (as it is),
and in addition variables such as zt, minz, maxz, akin to the color formatter
for lmt_contour.
This becomes handy when colors are to be aligned with function values (e.g.
negative = blue, zero = white, positive = red, see MWE attached).
- controlling line levels in lmt_contour
It would be convenient if certain levels could be set by the user. E.g. to make
sure the zero level contour line is included.
The user interface could potentially take a list, levels = { -1, -.5, 0, .5, 1
}, of contour level lines. See MWE attached.
From my understanding marching squares can do that. A possible reference
implementation could be QuadContourGenerator [1] in matplotlib, a bit of
description can be found in [2].
- colormaps
Contour plots often use rather complex colormaps, such as jet, rainbow or
veridis. They are optimized for perceptual resolution, color blindness,
screen/print or certain use cases.
The functionality is already there, but from a user's perspective, it would be
much easier if some of these were provided by the interface.
The interface could be color = "colormap('jet')(l/n)". Indeed, these are useful
in other use cases as well, such as bar charts, surface plots or shades.
One rudimentary example is in the attached file.
- number of levels in lmt_contour (potential bug)
The number of levels is different from the user's input. Depending on the
output range it can be lower or higher (see MWE attached).
Cheers,
Jacob Kauffmann
[1]
https://github.com/matplotlib/matplotlib/blob/96ff1146ad053c5c7481efd9de039c879a595968/src/_contour.cpp
[2]
https://github.com/matplotlib/matplotlib/blob/96ff1146ad053c5c7481efd9de039c879a595968/src/_contour.h
colors_and_contours_in_luametafun.tex
Description: Binary data
colors_and_contours_in_luametafun.pdf
Description: Adobe PDF document
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