[orx-palette] Add ColorBrewer2, demos, update README (#363)

orx-palette/src/jvmDemo/kotlin/DemoColorBrewer2_01.kt

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+import org.openrndr.application
+
+/**
+ * Demonstrates how to use a ColorBrewer2 palette.
+ * Finds the first available palette with 5 colors,
+ * then draws concentric circles filled with those colors.
+ */
+fun main() = application {
+    configure {
+        width = 720
+        height = 720
+    }
+    program {
+        val palette = colorBrewer2Palettes(numberOfColors = 5).first().colors
+        extend {
+            palette.forEachIndexed { i, color ->
+                drawer.fill = color
+                drawer.circle(drawer.bounds.center, 300.0 - i * 40.0)
+            }
+        }
+    }
+}

orx-palette/src/jvmDemo/kotlin/DemoColorBrewer2_02.kt

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+import org.openrndr.application
+import org.openrndr.color.ColorRGBa
+import org.openrndr.extra.shapes.primitives.Arc
+import org.openrndr.extra.shapes.primitives.grid
+
+/**
+ * Visualizes the ColorBrewer2 color palettes with 8 colors as circles
+ * made of colored arcs.
+ */
+fun main() = application {
+    configure {
+        width = 720
+        height = 720
+    }
+    program {
+        val palettes = colorBrewer2Palettes(numberOfColors = 8)
+        // Make a grid and discard some cells if there are more cells than palettes
+        val grid = drawer.bounds.grid(6, 6).flatten().take(palettes.size)
+        extend {
+            drawer.clear(ColorRGBa.WHITE)
+            // For each grid cell
+            grid.forEachIndexed { i, rect ->
+                // Find the corresponding palette
+                val palette = palettes[i].colors
+                // And display its colors on thick arcs
+                palette.forEachIndexed { ci, color ->
+                    drawer.strokeWeight = 15.0
+                    drawer.stroke = color
+                    drawer.fill = null
+                    drawer.contour(
+                        Arc(
+                            rect.center, rect.width * 0.35,
+                            360.0 * (ci + 0.0) / palette.size,
+                            360.0 * (ci + 1.0) / palette.size
+                        ).contour
+                    )
+                }
+            }
+        }
+    }
+}

orx-palette/src/jvmDemo/kotlin/DemoColorBrewer2_03.kt

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+import org.openrndr.application
+import org.openrndr.color.ColorRGBa
+import org.openrndr.extra.shapes.primitives.Arc
+import org.openrndr.extra.shapes.primitives.grid
+
+/**
+ * Visualizes 49 ColorBrewer2 color palettes of type "Diverging" as circles
+ * made of colored arcs. Since there are more palettes than grid cells,
+ * not all palettes are visualized.
+ */
+fun main() = application {
+    configure {
+        width = 720
+        height = 720
+    }
+    program {
+        val palettes = colorBrewer2Palettes(paletteType = ColorBrewer2Type.Diverging)
+        val grid = drawer.bounds.grid(7, 7).flatten().take(palettes.size)
+        extend {
+            drawer.clear(ColorRGBa.WHITE)
+            grid.forEachIndexed { i, rect ->
+                val palette = palettes[i].colors
+                palette.forEachIndexed { ci, color ->
+                    drawer.strokeWeight = 15.0
+                    drawer.stroke = color
+                    drawer.fill = null
+                    drawer.contour(
+                        Arc(
+                            rect.center, rect.width * 0.4,
+                            360.0 * (ci + 0.0) / palette.size,
+                            360.0 * (ci + 1.0) / palette.size
+                        ).contour
+                    )
+                }
+            }
+        }
+    }
+}

orx-palette/src/jvmDemo/kotlin/DemoPaletteStudio01.kt

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+import org.openrndr.application
+import org.openrndr.extra.palette.PaletteStudio
+
+/**
+ * Demonstrates how to access palette colors using PaletteStudio.
+ * A new random palette is loaded every 60 animation frames.
+ */
+fun main() = application {
+    configure {
+        width = 720
+        height = 720
+    }
+    program {
+        val paletteStudio = PaletteStudio()
+
+        // Choose a specific initial palette
+        paletteStudio.select(11)
+
+        extend {
+            if(frameCount % 60 == 50) {
+                paletteStudio.randomPalette()
+            }
+            drawer.clear(paletteStudio.background)
+
+            paletteStudio.colors2.forEachIndexed { i, color ->
+                drawer.fill = color
+                drawer.circle(drawer.bounds.center, 300.0 - i * 40.0)
+            }
+        }
+    }
+}

orx-palette/src/jvmDemo/kotlin/DemoPaletteStudio02.kt

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+import org.openrndr.application
+import org.openrndr.color.ColorRGBa
+import org.openrndr.extra.palette.PaletteStudio
+
+/**
+ * Demonstrates how to create a design using PaletteStudio.
+ * Press the `c` key to load a random palette.
+ *
+ */
+fun main() = application {
+    configure {
+        title = "Palette"
+        width = 720
+        height = 720
+    }
+    program {
+        val paletteStudio = PaletteStudio()
+
+        val colors = mutableListOf<ColorRGBa>()
+
+        fun fillColors() {
+            for (n in 0..36) {
+                when (n) {
+                    12 -> paletteStudio.loadCollection(PaletteStudio.Collections.TWO)
+                    24 -> paletteStudio.loadCollection(PaletteStudio.Collections.THREE)
+                }
+
+                val color = paletteStudio.colors.random()
+
+                colors.add(color)
+            }
+        }
+
+        keyboard.keyDown.listen {
+            if (it.name == "c") {
+                colors.clear()
+                fillColors()
+            }
+        }
+
+        fillColors()
+
+        extend {
+            drawer.clear(paletteStudio.background)
+
+            val size = 120.0
+            val radius = size / 2.0
+
+            for (x in 0 until 6) {
+                for (y in 0 until 6) {
+                    val index = x + y * 6
+                    val color = colors[index]
+                    val x = size * x
+                    val y = size * y
+
+                    drawer.fill = color
+                    drawer.stroke = color
+
+                    if (index <= 11 || index > 23) {
+                        drawer.circle(x + radius, y + radius, radius)
+                    } else {
+                        drawer.rectangle(x, y, size, size)
+                    }
+                }
+            }
+        }
+    }
+}