Pien-Studio/apps/web/lib/effects/face-blur.ts

import type { FaceBlurEffect } from "@pien-studio/types";
import type { EffectRenderer, EffectRenderContext } from "./types";

function drawPixelatedRegion(
  ctx: CanvasRenderingContext2D,
  source: CanvasImageSource,
  sourceX: number,
  sourceY: number,
  sourceWidth: number,
  sourceHeight: number,
  targetX: number,
  targetY: number,
  targetWidth: number,
  targetHeight: number,
  blockSize: number,
) {
  const sampleCanvas = document.createElement("canvas");
  sampleCanvas.width = Math.max(1, Math.round(targetWidth / blockSize));
  sampleCanvas.height = Math.max(1, Math.round(targetHeight / blockSize));
  const sampleCtx = sampleCanvas.getContext("2d");
  if (!sampleCtx) return;
  sampleCtx.imageSmoothingEnabled = false;
  sampleCtx.drawImage(source, sourceX, sourceY, sourceWidth, sourceHeight, 0, 0, sampleCanvas.width, sampleCanvas.height);
  ctx.imageSmoothingEnabled = false;
  ctx.drawImage(sampleCanvas, 0, 0, sampleCanvas.width, sampleCanvas.height, targetX, targetY, targetWidth, targetHeight);
  ctx.imageSmoothingEnabled = true;
}

function drawBlurredRegionFallback(
  ctx: CanvasRenderingContext2D,
  source: CanvasImageSource,
  sourceX: number,
  sourceY: number,
  sourceWidth: number,
  sourceHeight: number,
  targetX: number,
  targetY: number,
  targetWidth: number,
  targetHeight: number,
  amount: number,
) {
  const regionCanvas = document.createElement("canvas");
  regionCanvas.width = Math.max(1, Math.round(targetWidth));
  regionCanvas.height = Math.max(1, Math.round(targetHeight));
  const regionCtx = regionCanvas.getContext("2d");
  if (!regionCtx) return;
  regionCtx.drawImage(source, sourceX, sourceY, sourceWidth, sourceHeight, 0, 0, regionCanvas.width, regionCanvas.height);
  const scale = Math.max(0.04, Math.min(0.5, 1 / Math.max(2, amount / 2)));
  const blurCanvas = document.createElement("canvas");
  blurCanvas.width = Math.max(1, Math.round(regionCanvas.width * scale));
  blurCanvas.height = Math.max(1, Math.round(regionCanvas.height * scale));
  const blurCtx = blurCanvas.getContext("2d");
  if (!blurCtx) return;
  blurCtx.imageSmoothingEnabled = true;
  blurCtx.drawImage(regionCanvas, 0, 0, blurCanvas.width, blurCanvas.height);
  for (let i = 0; i < 3; i++) {
    regionCtx.clearRect(0, 0, regionCanvas.width, regionCanvas.height);
    regionCtx.drawImage(blurCanvas, 0, 0, blurCanvas.width, blurCanvas.height, 0, 0, regionCanvas.width, regionCanvas.height);
    blurCtx.clearRect(0, 0, blurCanvas.width, blurCanvas.height);
    blurCtx.drawImage(regionCanvas, 0, 0, regionCanvas.width, regionCanvas.height, 0, 0, blurCanvas.width, blurCanvas.height);
  }
  ctx.drawImage(regionCanvas, 0, 0, regionCanvas.width, regionCanvas.height, targetX, targetY, targetWidth, targetHeight);
}

function renderRegions(
  ctx: CanvasRenderingContext2D,
  image: HTMLImageElement,
  effect: FaceBlurEffect,
  targetWidth: number,
  targetHeight: number,
) {
  if (!effect.regions.length) return;
  const legacyScaleX = image.naturalWidth / Math.max(1, targetWidth);
  const legacyScaleY = image.naturalHeight / Math.max(1, targetHeight);

  for (const region of effect.regions) {
    const sourceWidth = region.sourceWidth ?? 0;
    const sourceHeight = region.sourceHeight ?? 0;
    const hasSourceDims = sourceWidth > 0 && sourceHeight > 0;
    const scaleX = hasSourceDims ? targetWidth / sourceWidth : 1;
    const scaleY = hasSourceDims ? targetHeight / sourceHeight : 1;

    const x = Math.max(0, Math.floor(region.x * scaleX));
    const y = Math.max(0, Math.floor(region.y * scaleY));
    const w = Math.max(1, Math.floor(region.width * scaleX));
    const h = Math.max(1, Math.floor(region.height * scaleY));
    const sx0 = hasSourceDims ? region.x : Math.max(0, Math.floor(region.x * legacyScaleX));
    const sy0 = hasSourceDims ? region.y : Math.max(0, Math.floor(region.y * legacyScaleY));
    const sw = hasSourceDims ? region.width : Math.max(1, Math.floor(region.width * legacyScaleX));
    const sh = hasSourceDims ? region.height : Math.max(1, Math.floor(region.height * legacyScaleY));

    if (effect.method === "censor") {
      ctx.fillStyle = region.censorColor ?? effect.censorColor ?? "#111111";
      ctx.fillRect(x, y, w, h);
      continue;
    }
    if (effect.method === "pixelate") {
      drawPixelatedRegion(ctx, image, sx0, sy0, sw, sh, x, y, w, h, Math.max(4, Math.round(effect.amount / 2)));
      continue;
    }
    if ("filter" in ctx && typeof ctx.filter === "string") {
      ctx.save();
      ctx.filter = `blur(${effect.amount}px)`;
      ctx.drawImage(image, sx0, sy0, sw, sh, x, y, w, h);
      ctx.restore();
      continue;
    }
    drawBlurredRegionFallback(ctx, image, sx0, sy0, sw, sh, x, y, w, h, effect.amount);
  }
}

function renderLayer(context: EffectRenderContext, effect: FaceBlurEffect) {
  const { ctx, image, targetWidth, targetHeight } = context;
  if (!effect.regions.length) {
    ctx.drawImage(image, 0, 0, targetWidth, targetHeight);
    return;
  }

  const allHaveSourceDims = effect.regions.every((r) => (r.sourceWidth ?? 0) > 0 && (r.sourceHeight ?? 0) > 0);
  if (!allHaveSourceDims) {
    ctx.drawImage(image, 0, 0, targetWidth, targetHeight);
    renderRegions(ctx, image, effect, targetWidth, targetHeight);
    return;
  }

  const sourceCanvas = document.createElement("canvas");
  sourceCanvas.width = Math.max(1, image.naturalWidth);
  sourceCanvas.height = Math.max(1, image.naturalHeight);
  const sourceCtx = sourceCanvas.getContext("2d");
  if (!sourceCtx) {
    ctx.drawImage(image, 0, 0, targetWidth, targetHeight);
    return;
  }
  sourceCtx.drawImage(image, 0, 0, sourceCanvas.width, sourceCanvas.height);
  renderRegions(sourceCtx, image, effect, sourceCanvas.width, sourceCanvas.height);
  ctx.drawImage(sourceCanvas, 0, 0, sourceCanvas.width, sourceCanvas.height, 0, 0, targetWidth, targetHeight);
}

export const faceBlurRenderer: EffectRenderer = {
  kind: "face-blur",
  render: ({ ctx, image, targetWidth, targetHeight }, effect) => {
    renderRegions(ctx, image, effect, targetWidth, targetHeight);
  },
  renderLayer,
};