🎉 お絵かきキャンバス実装

apps/client/app/features/artboard/bucketFill.ts

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+// ref: https://github.com/cat-crosswalk/nascalay-frontend/blob/main/src/components/Canvas/bucketFill.ts
+
+import {
+  type Color,
+  type LikeEqualColor,
+  colorsToRaw,
+  equalColor,
+  hexToColor,
+  rawToColors,
+} from "./utils";
+
+// https://nullpon.moe/dev/sample/canvas/bucketfill.html めちゃめちゃ参考にしてる
+// シードフィルアルゴリズムで塗りつぶす
+
+/**
+ * 指定された座標から右方向にまっすぐ targetColor と等しい色を塗りつぶす
+ *
+ * @returns 右端の x 座標
+ */
+function drawToRight(
+  data: Color[][],
+  x: number,
+  y: number,
+  color: Color,
+  widthRange: readonly [number, number],
+  targetColor: Color,
+  likeEqualColor: LikeEqualColor,
+) {
+  let rightEnd = null;
+  for (let nowX = x + 1; nowX < widthRange[1]; nowX++) {
+    const nowColor = data[y][nowX];
+    if (!likeEqualColor(nowColor, targetColor)) break;
+    data[y][nowX] = color;
+    rightEnd = nowX;
+  }
+  return rightEnd;
+}
+
+/**
+ * 指定された座標から左方向にまっすぐ targetColor と等しい色を塗りつぶす
+ *
+ * @returns 左端の x 座標
+ */
+function drawToLeft(
+  data: Color[][],
+  x: number,
+  y: number,
+  color: Color,
+  widthRange: readonly [number, number],
+  targetColor: Color,
+  likeEqualColor: LikeEqualColor,
+) {
+  let leftEnd = null;
+  for (let nowX = x; nowX >= widthRange[0]; nowX--) {
+    const nowColor = data[y][nowX];
+    if (!likeEqualColor(nowColor, targetColor)) break;
+    data[y][nowX] = color;
+    leftEnd = nowX;
+  }
+  return leftEnd;
+}
+
+/**
+ * seeds を破壊的に更新する
+ */
+function updateSeeds(
+  data: Readonly<Color[][]>,
+  xLeft: number,
+  xRight: number,
+  y: number,
+  seeds: { x: number; y: number }[],
+  targetColor: Color,
+  heightRange: readonly [number, number],
+  likeEqualColor: LikeEqualColor,
+) {
+  if (y < heightRange[0] || y >= heightRange[1]) return;
+
+  let prevIsTarget = false;
+  for (let nowX = xLeft; nowX <= xRight; nowX++) {
+    const nowColor = data[y][nowX];
+    if (likeEqualColor(nowColor, targetColor)) {
+      if (!prevIsTarget) {
+        seeds.push({ x: nowX, y });
+      }
+      prevIsTarget = true;
+    } else {
+      prevIsTarget = false;
+    }
+  }
+}
+
+export function bucketFill(
+  canvas: HTMLCanvasElement,
+  x: number,
+  y: number,
+  color: `#${string}`,
+  widthRange?: [number, number],
+  heightRange?: [number, number],
+  likeEqualColor: LikeEqualColor = equalColor,
+) {
+  const ctx = canvas.getContext("2d");
+  if (ctx === null) {
+    return;
+  }
+
+  const width = canvas.width;
+  const height = canvas.height;
+  const imageData = ctx.getImageData(0, 0, width, height);
+  const data = imageData.data;
+  const formattedData = rawToColors(data, width, height);
+  const targetColor = formattedData[y][x];
+  const colorObj = hexToColor(color);
+  if (colorObj === null) {
+    console.error("invalid color");
+    return;
+  }
+  if (likeEqualColor(colorObj, targetColor)) return;
+
+  const xRange = widthRange ?? [0, width];
+  const yRange = heightRange ?? [0, height];
+
+  const seeds = [{ x, y }];
+  while (seeds.length > 0) {
+    // biome-ignore lint/style/noNonNullAssertion: while の条件式から pop は undefined にならない
+    const { x, y } = seeds.pop()!;
+
+    // 左右に塗りつぶす
+    const leftX =
+      drawToLeft(
+        formattedData,
+        x,
+        y,
+        colorObj,
+        xRange,
+        targetColor,
+        likeEqualColor,
+      ) ?? x;
+    const rightX =
+      drawToRight(
+        formattedData,
+        x,
+        y,
+        colorObj,
+        xRange,
+        targetColor,
+        likeEqualColor,
+      ) ?? x;
+
+
+    updateSeeds(
+      formattedData,
+      leftX,
+      rightX,
+      y + 1,
+      seeds,
+      targetColor,
+      yRange,
+      likeEqualColor,
+    );
+    updateSeeds(
+      formattedData,
+      leftX,
+      rightX,
+      y - 1,
+      seeds,
+      targetColor,
+      yRange,
+      likeEqualColor,
+    );
+  }
+
+  imageData.data.set(colorsToRaw(formattedData, width, height));
+  ctx.putImageData(imageData, 0, 0);
+}

apps/client/app/features/artboard/index.tsx

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+import styled from "@emotion/styled";
+import type { RefObject } from "react";
+import type { MouseHandlers } from "./types";
+
+interface Props {
+  canvasRef: RefObject<HTMLCanvasElement>;
+  mouseHandlers: MouseHandlers;
+  isLocked?: boolean;
+}
+
+export function Artboard({ canvasRef, mouseHandlers, isLocked }: Props) {
+  return <Canvas ref={canvasRef} width={640} height={480} {...mouseHandlers} />;
+}
+
+const Canvas = styled.canvas`
+  border: 1px solid black;
+`;

apps/client/app/features/artboard/types.ts

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+export const penTypes = ["pen", "eraser", "bucket"] as const;
+export type PenType = (typeof penTypes)[number];
+
+export interface Pos {
+  x: number;
+  y: number;
+}
+
+export type MouseHandlers = Required<
+  Pick<
+    React.DOMAttributes<HTMLElement>,
+    "onMouseDown" | "onMouseMove" | "onMouseUp" | "onMouseOut" | "onMouseEnter"
+  >
+>;
+
+/**
+ * 色を扱いやすくするための型
+ * r, g, b, a はそれぞれ 0 から 255 の範囲の整数
+ */
+export interface Color {
+  r: number;
+  g: number;
+  b: number;
+  a: number;
+}
+export type LikeEqualColor = (a: Color, b: Color) => boolean;

apps/client/app/features/artboard/useArtboard.ts

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+import type React from "react";
+import { type RefObject, useCallback, useRef } from "react";
+import type { MouseHandlers, Pos } from "./types";
+import { useHistory } from "./useHistory";
+import { type PenData, useSketch } from "./useSketch";
+import { type CanvasData, applyCanvasData, getCanvasData } from "./utils";
+
+interface Handler {
+  clear(): void;
+  undo(): void;
+  redo(): void;
+  resetCanvas(): void;
+  shortcut(e: React.KeyboardEvent): void;
+  exportDataURL(): string;
+  canRedo: boolean;
+  canUndo: boolean;
+  mouseHandlers: MouseHandlers;
+}
+
+interface State {
+  lastPos: Pos | null;
+}
+const createInitialState = (): State => ({
+  lastPos: null,
+});
+
+export function useArtboard(
+  canvasRef: RefObject<HTMLCanvasElement>,
+  penData: PenData,
+): Handler {
+  // NOTE: initial state が重くなる場合は https://ja.react.dev/reference/react/useRef#avoiding-recreating-the-ref-contents のようにする
+  const state = useRef<State>(createInitialState());
+  const {
+    canRedo,
+    canUndo,
+    clearHistory,
+    pushHistory,
+    undoHistory,
+    redoHistory,
+  } = useHistory<CanvasData>();
+  const { mouseHandlers } = useSketch(canvasRef, penData, pushHistory);
+
+  const resetCanvas = useCallback(() => {
+    const canvas = canvasRef.current;
+    if (canvas === null) return;
+    const ctx = canvas.getContext("2d");
+    if (ctx === null) return;
+
+    ctx.clearRect(0, 0, canvas.width, canvas.height);
+    state.current = createInitialState();
+
+    clearHistory();
+  }, [canvasRef.current, clearHistory]);
+
+  const saveCanvas = useCallback(() => {
+    const canvas = canvasRef.current;
+    if (canvas === null) return;
+
+    const savedData = getCanvasData(canvas);
+    if (savedData === null) return;
+
+    pushHistory(savedData);
+  }, [canvasRef.current, pushHistory]);
+
+  const undo = useCallback(() => {
+    const canvas = canvasRef.current;
+    if (canvas === null) return;
+
+    const now = getCanvasData(canvas);
+    if (now === null) return;
+
+    const next = undoHistory(now);
+    if (next === null) return;
+
+    applyCanvasData(canvas, next);
+  }, [canvasRef.current, undoHistory]);
+
+  const redo = useCallback(() => {
+    const canvas = canvasRef.current;
+    if (canvas === null) return;
+
+    const now = getCanvasData(canvas);
+    if (now === null) return;
+
+    const next = redoHistory(now);
+    if (next === undefined) return;
+
+    applyCanvasData(canvas, next);
+  }, [canvasRef.current, redoHistory]);
+
+  const clear = useCallback(() => {
+    const canvas = canvasRef.current;
+    if (canvas === null) return;
+
+    saveCanvas();
+
+    const ctx = canvas.getContext("2d");
+    if (ctx === null) return;
+
+    ctx.clearRect(0, 0, canvas.width, canvas.height);
+  }, [canvasRef.current, saveCanvas]);
+
+  const shortcut = useCallback(
+    (e: React.KeyboardEvent) => {
+      // NOTE: shift を押した状態だと e.key が大文字になるので小文字に変換してから比較する
+      if (e.key.toLocaleLowerCase() === "z" && (e.ctrlKey || e.metaKey)) {
+        if (e.shiftKey) {
+          redo();
+        } else {
+          undo();
+        }
+      }
+    },
+    [redo, undo],
+  );
+
+  const exportDataURL = useCallback(() => {
+    const canvas = canvasRef.current;
+    if (canvas === null) return "";
+
+    return canvas.toDataURL();
+  }, [canvasRef.current]);
+
+  return {
+    clear,
+    undo,
+    redo,
+    resetCanvas,
+    shortcut,
+    exportDataURL,
+    canRedo,
+    canUndo,
+    mouseHandlers,
+  };
+}