function processImage(originalImg, strokeSize = "5", intensity = "3") {
let blurNum = Math.max(0, Math.min(Number(strokeSize) || 5, 100));
let darkenNum = Math.max(0, Math.min(Number(intensity) || 3, 20));
const w = originalImg.width;
const h = originalImg.height;
// Create a flattened source canvas to avoid issues with transparent PNGs
const srcCanvas = document.createElement('canvas');
srcCanvas.width = w;
srcCanvas.height = h;
const sCtx = srcCanvas.getContext('2d');
// Fill background with white, then draw original image over it
sCtx.fillStyle = '#ffffff';
sCtx.fillRect(0, 0, w, h);
sCtx.drawImage(originalImg, 0, 0, w, h);
// Create a base canvas for the core sketch effect
// Uses the classic Color Dodge blend of grayscale + inverted blurred grayscale
const baseCanvas = document.createElement('canvas');
baseCanvas.width = w;
baseCanvas.height = h;
const bCtx = baseCanvas.getContext('2d');
// Draw base grayscale version
bCtx.filter = 'grayscale(100%)';
bCtx.drawImage(srcCanvas, 0, 0, w, h);
// Apply color-dodge and render the inverted & blurred layer
bCtx.globalCompositeOperation = 'color-dodge';
bCtx.filter = `grayscale(100%) invert(100%) blur(${blurNum}px)`;
bCtx.drawImage(srcCanvas, 0, 0, w, h);
// Final canvas to adjust edge darkness/intensity
const finalCanvas = document.createElement('canvas');
finalCanvas.width = w;
finalCanvas.height = h;
const fCtx = finalCanvas.getContext('2d');
// Draw the initial light sketch
fCtx.drawImage(baseCanvas, 0, 0, w, h);
// Switch to multiply blend mode to darken pencil strokes without muddying whites
fCtx.globalCompositeOperation = 'multiply';
// Layer multiple times based on requested intensity
for (let i = 0; i < darkenNum; i++) {
fCtx.drawImage(baseCanvas, 0, 0, w, h);
}
return finalCanvas;
}The Image Pencil Drawing Tool transforms standard photographs into stylized pencil sketches. By utilizing adjustable stroke size and intensity settings, users can control the blur and darkness of the resulting drawing to achieve different artistic effects. This tool is useful for creative photo editing, creating artistic avatars, or converting portraits into hand-drawn style illustrations for social media and digital art projects.