Add documentation page for extracting colors.

PiperOrigin-RevId: 562742819

Author: Material Eng

extract_colors.md

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+# Extracting colors from an image
+
+[TOC]
+
+To extract colors from an image that are suitable for generating schemes, use
+the `quantize` and `score` libraries.
+
+TODO: Insert here a diagram for image-to-colors extraction.
+
+## Step 1 — Image to Pixels
+
+First, convert an image into **an array of pixels in ARGB
+format**. MCU does not provide this feature; please use the idiomatic method
+provided by your language.
+
+For example, in Java, one may use the `BufferedImage.getRGB` method:
+
+```java
+import java.awt.image.BufferedImage;
+
+class ImageUtils {
+  // ...
+
+  public static int[] imageToPixels(BufferedImage image) {
+    int width = image.getWidth();
+    int height = image.getHeight();
+    BufferedImage outputImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
+    return image.getRGB(0, 0, width, height, null, 0, width);
+  }
+}
+```
+
+## Step 2 — Pixels to Prominent Colors
+
+Once you have the array of pixels, pass it into `QuantizerCelebi.quantize`
+provided by the `quantize` library.
+
+<section>
+
+###### Dart
+
+```dart
+final quantizerResult = await QuantizerCelebi.quantize(pixels, maxColors);
+```
+
+###### Java
+
+```java
+QuantizerResult quantizerResult = QuantizerCelebi.quantize(pixels, maxColors);
+```
+
+###### TypeScript
+
+```typescript
+const quantizerResult = QuantizerCelebi.quantize(pixels, maxColors);
+```
+
+###### C++
+
+```cpp
+QuantizerResult quantizer_result = QuantizeCelebi(pixels, max_colors);
+```
+
+###### Swift
+
+```swift
+let quantizerResult = QuantizerCelebi().quantize(pixels, maxColors)
+```
+
+</section>
+
+The parameter `maxColors` is a limit on the number of colors returned by the
+quantizer. A reasonable default is 128.
+
+## Step 3 — Prominent Colors to Suitable Seed Colors
+
+Use the `Score.score` method provided by the `score` library to extract colors
+that are suitable as seeds for color schemes, ranked by decreasing suitability.
+
+<section>
+
+###### Dart
+
+```dart
+final colors = Score.score(quantizerResult.colorToCount);
+```
+
+###### Java
+
+```java
+List<Integer> colors = Score.score(quantizerResult);
+```
+
+###### TypeScript
+
+```typescript
+final colors = Score.score(quantizerResult);
+```
+
+###### C++
+
+```cpp
+std::vector<Argb> colors = RankedSuggestions(quantizer_result.color_to_count);
+```
+
+###### Swift
+
+```swift
+let colors = Score.score(quantizerResult.colorToCount)
+```
+
+</section>

sitemap.md

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+*   [Home](README.md)
+
+Sitemap
+
+*   I want to …
+
+    -   [Extract colors from an image](extract_colors.md)