I would like to color an image generated from some data, using two color schemes based on two ranges of the data. This is my attempt:
Image[RandomReal[1, {10, 10}],
ColorFunction -> (Piecewise[{{ColorData["AlpineColors"][#], 0 < # < .5},
{ColorData["SouthwestColors"][#], .5 < # < 1}}] &)]]
Here is something 10 x faster.
I made the same assumption as george2079 so for each subinterval whole color scheme is used not just exact part like in Simon's answer. Maybe useful, maybe not.
colorF ~ createColorFunction ~ {"TemperatureMap", "AvocadoColors"};
pic = Image@ConstantArray[Range[0, 1, .001], 100]
Colorize[pic, ColorFunction -> colorF]
It is quite general, you can use arbitrary set of schemes:
colorF ~ createColorFunction ~ {"AlpineColors", "AvocadoColors",
"TemperatureMap", "SouthwestColors"};
Colorize[pic, ColorFunction -> colorF]
colorF ~ createColorFunction ~ RandomSample[ColorData["Gradients"], 10];
Colorize[pic, ColorFunction -> colorF]
colorF ~ createColorFunction ~ RandomSample[ColorData["Gradients"], 2];
Colorize[#, ColorFunction -> colorF, ColorFunctionScaling -> False] &@
ColorConvert[ExampleData[{"TestImage", "Lena"}], "Grayscale"]
The problem is condition which has to be checked for each pixel. We can take a walk around,
SetAttributes[createColorFunction, HoldFirst];
createColorFunction[functionname_, schemes_List] := Module[{
colorss, setsNum, setsLength
},
Blend[{Red},1]; (*initialize `Color` stuff*)
colorss = DataPaclets`ColorDataDump`getColorSchemeData[#][[5]] & /@ schemes;
setsNum = Length@colorss;
setsLength = Length /@ colorss;
functionname = With[{colorSets = Transpose[{
Accumulate[
Join @@ Table[
PadRight[{0}, setsLength[[i]],
1./((setsLength[[i]] - 1) setsNum)], {i, setsNum}]],
Join @@ colorss}]
},
Blend[colorSets, #] &
]
]
The ugly code in Accumulate takes lists of colors and creates:
{{c11, c12, c13}, {c21, c22, c23, c24, c25}}
------------->
{
{0, 0.25, 0.5, 0.5, 0.625, 0.75, 0.875, 1.},
{c11, c12, c13, c21, c22, c23, c24, c25}
} //Transpose
Which can be used to create Blend arguments. Colors sets are given by Blend code for built-in ColorData schemes
You can use Colorize for this
Colorize[RandomImage[1, {10, 10}], ColorFunction -> (Piecewise[
{{ColorData["AlpineColors"][#], 0 < # < .5},
{ColorData["SouthwestColors"][#], .5 < # < 1}}] &)]
RandomImage[1, {100, 100}] takes around 10s but for Image@ConstantArray[Range[0, 1, .01], 100] only 0.5s. It is not related to the type of data because ColorFunction -> (Blend[{Blue, Red}, #] &) is fast for both. I tried your code with the first setup, that is why I commited to manual approach, which seems to be an overkill probably. Do you know what is going on?
– Kuba
Mar 05 '15 at 20:26
renderImage function for this sort of thing.
– Simon Woods
Mar 05 '15 at 22:04
Here is a slightly compacted re-implementation of Kuba's routine. Its only caveat is that it will not work for gradients with non-equispaced colors, like "BrightBands"; the routine can be modified for that case, but it will be a bit more complicated.
chimeraColors[cols : {__String}] := Module[{bl, cl},
cl = ColorData[#, "BlendArgument"] & /@ cols;
If[! MatchQ[cl, {cc__?(VectorQ[#, ColorQ] &)}], Return[$Failed]];
bl = Transpose[Join @@@ {MapThread[Rescale[#1, {0, 1}, #2] &,
{Subdivide[Length[#] - 1] & /@ cl,
Partition[Subdivide[Length[cl]], 2, 1]}], cl}];
With[{c = bl}, Blend[c, #] &]]
Some examples:
cfun = chimeraColors[{"DeepSeaColors", "ThermometerColors", "SolarColors"}];
LinearGradientImage[cfun, {600, 60}]
cfun = chimeraColors[{"Pastel", "CMYKColors"}];
Colorize[ExampleData[{"Texture", "Bubbles"}], ColorFunction -> cfun,
ColorFunctionScaling -> False]
Added 6/30/2016
I present here a routine for the generalization of the OP's desire to use different color gradients in different intervals. This avoids the slowness observed by Kuba and the Wizard by directly constructing a Blend[] function from stitched-together pieces of the component color gradients. Here it is:
bricolage[lst : {{_?NumericQ, _String} ..}] := Module[{cc, cl, dc, dl, gl, il, kl, nl},
{nl, gl} = Transpose[SortBy[lst, First]];
If[! (And @@ Thread[0 <= nl <= 1]) ||
Complement[gl, DataPaclets`ColorDataDump`gradientSchemeNames] =!= {},
Return[$Failed]];
nl = Sort[nl]; If[Last[nl] != 1, AppendTo[nl, 1]];
cl = ColorData[#, "BlendArgument"] & /@ gl;
If[MemberQ[cl, l_ /; ! VectorQ[l, ColorQ]], Return[$Failed]];
kl = (Length /@ cl) - 1; dl = Subdivide /@ kl; il = Partition[nl, 2, 1];
dc = MapThread[Take[#1, Floor[#2 #3] + {2, 1}] &, {dl, il, kl}];
cc = MapThread[Take[#1, Floor[#2 #3] + {2, 1}] &, {cl, il, kl}];
cc = MapThread[Flatten[{If[#1[[1]] != #3[[1]],
ColorData[#4, #3[[1]]], Nothing],
#2,
If[#1[[-1]] != #3[[-1]],
ColorData[#4, #3[[-1]]], Nothing]}] &,
{dc, cc, il, gl}];
dc = MapThread[Union[Flatten[Insert[#2, #1, 2]]] &, {dc, il}];
With[{l = Flatten[{dc, cc}, {{2, 3}, {1}}]}, Blend[l, #] &]]
At the moment, the routine does not support color gradients where the colors are not equispaced (e.g. "BrightBands" or "M10DefaultDensityGradient"). Otherwise, it works quite well:
(* OP's color function *)
cfun = bricolage[{{0, "AlpineColors"}, {1/2, "SouthwestColors"}}];
LinearGradientImage[cfun, {600, 60}]
cfun = bricolage[{{0, "IslandColors"}, {2/5, "LightTerrain"}, {3/4, "SandyTerrain"}}];
Colorize[ExampleData[{"Texture", "Bubbles"}], ColorFunction -> cfun,
ColorFunctionScaling -> False]
One approach:
ImageApply[
List @@ Piecewise[{
{ColorData["AlpineColors"][2 #], 0 < # < .5},
{ColorData["SouthwestColors"][2 # - 1 ], .5 < # < 1}
}] &, Image[RandomReal[1, {10, 10}]]]
or
Image[Map[
List @@ Piecewise[{
{ColorData["AlpineColors"][2 #], 0 < # < .5},
{ColorData["SouthwestColors"][2 # - 1 ], .5 < # < 1}}] & ,
RandomReal[1, {100, 100}], {2}]]
( identical timing .. )
This is simply the correct version of your original approach:
Graphics[{Raster[RandomReal[1, {10, 10}],
ColorFunction -> (Piecewise[{{ColorData["AlpineColors"][#],
0 < # < .5}, {ColorData["SouthwestColors"][#], .5 < # < 1}}] &)]}]
ColorFunction is an option of Raster, Image has no such option.
ArrayPlot[RandomReal[1, {10, 10}], ColorFunction -> (Piecewise[{{ColorData["LightTerrain"][#], 0 < # < .5}, {ColorData["TemperatureMap"][#], .5 < # < 1}}] &), Frame -> None]– Dr. belisarius Mar 04 '15 at 20:39