CODEWITHSUNDEEP
graphicswolfram-mathematica
500
500

Reputation: 6629

Conditional coloring based on a gradient

Please consider :

Manipulate[
Row[{
Graphics[Disk[]], 
Graphics[{
 Polygon[{{0, 0}, {3, 0}, {3, 1}, {0, 1}},
 VertexColors -> {White, Blend[{White, Blue}], 
 Blend[{White, Blue}], White}],
 Black, Thick,
 Line[{{i, 0}, {i, 1}}]}, ImageSize -> 300]}], 
{i, 0, 3}]

enter image description here

Using Szabolcs`s solution on Gradient Filling

How could I color the disk with the color located underneath the Black Line ?

Upvotes: 5

Views: 285

Answers (2)

Verbeia
Verbeia

Reputation: 4420

If you need to do this for a blend of colours other than something and white, Opacity won't be suitable. You could instead stay closer to Szabolcs' original solution using the second argument to Blend like so:

skyBlue = Blend[{White,Blue}];
Manipulate[ Row[{ Graphics[{Blend[{White,skyBlue},i/3], Disk[]}],  
 Graphics[{  Polygon[{{0, 0}, {3, 0}, {3, 1}, {0, 1}},  
 VertexColors -> {White, skyBlue,   
 skyBlue, White}],  Black, Thick,  
 Line[{{i, 0}, {i, 1}}]}, ImageSize -> 300]}],  {i, 0, 3}]

I have divided i by 3 because that parameter is meant to vary between 0 and 1.

enter image description here

Upvotes: 6

abcd
abcd

Reputation: 42245

Here is one solution which works because the color on the left is White and the gradient is linear.

With[{max = 3, color = Blend[{White, Blue}]}, 
 Manipulate[
  Row[{Graphics[{Opacity[i/max], color, Disk[]}], 
    Graphics[{Polygon[{{0, 0}, {max, 0}, {max, 1}, {0, 1}}, 
       VertexColors -> {White, color, color, White}], Black, Thick, 
      Line[{{i, 0}, {i, 1}}]}, ImageSize -> 300]}], {i, 0, max}]]

enter image description here

If you had two different colors for each end (i.e., something other than White), the Opacity approach won't work. Instead, you can use the optional blending fraction argument to Blend the colors in the desired proportion. Here's an example:

With[{max = 3, color1 = Red, color2 = Green}, 
 Manipulate[
  Row[{Graphics[{Blend[{color1, color2}, i/max], Disk[]}], 
    Graphics[{Polygon[{{0, 0}, {max, 0}, {max, 1}, {0, 1}}, 
       VertexColors -> {color1, color2, color2, color1}], Black, 
      Thick, Line[{{i, 0}, {i, 1}}]}, ImageSize -> 300]}], {i, 0, 
   max}]]

enter image description here

Upvotes: 7

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