import { Jimp } from "jimp";
export interface CompressOptions {
maxWidth?: number;
maxHeight?: number;
quality?: number;
maxSizeBytes?: number;
}
const DEFAULT_OPTIONS: CompressOptions = {
maxWidth: 800, // Safe for API limit of 2000px
maxHeight: 1400, // Safe for API limit of 2000px
quality: 70,
maxSizeBytes: 1024 * 1024, // 1MB max for base64 (safe margin for API)
};
/**
* Compress PNG image buffer
* - Resize if larger than max dimensions
* - Convert to JPEG with specified quality
* - Iteratively reduce quality if still too large
* Returns base64 encoded JPEG
*/
export async function compressScreenshot(
pngBuffer: Buffer,
options: CompressOptions = {}
): Promise<{ data: string; mimeType: string }> {
const opts = { ...DEFAULT_OPTIONS, ...options };
const image = await Jimp.read(pngBuffer);
const width = image.width;
const height = image.height;
// Calculate new dimensions maintaining aspect ratio
let newWidth = width;
let newHeight = height;
if (width > opts.maxWidth! || height > opts.maxHeight!) {
const widthRatio = opts.maxWidth! / width;
const heightRatio = opts.maxHeight! / height;
const ratio = Math.min(widthRatio, heightRatio);
newWidth = Math.round(width * ratio);
newHeight = Math.round(height * ratio);
}
// Resize if needed
if (newWidth !== width || newHeight !== height) {
image.resize({ w: newWidth, h: newHeight });
}
// Convert to JPEG with iterative quality reduction if needed
let quality = opts.quality!;
let jpegBuffer: Buffer;
let attempts = 0;
const maxAttempts = 5;
do {
jpegBuffer = await image.getBuffer("image/jpeg", { quality });
// Check if size is within limit
if (jpegBuffer.length <= opts.maxSizeBytes!) {
break;
}
// Reduce quality and try again
quality = Math.max(20, quality - 15);
attempts++;
} while (attempts < maxAttempts);
// If still too large after quality reduction, resize further
if (jpegBuffer.length > opts.maxSizeBytes!) {
const scaleFactor = Math.sqrt(opts.maxSizeBytes! / jpegBuffer.length) * 0.9;
const smallerWidth = Math.round(newWidth * scaleFactor);
const smallerHeight = Math.round(newHeight * scaleFactor);
image.resize({ w: smallerWidth, h: smallerHeight });
jpegBuffer = await image.getBuffer("image/jpeg", { quality: 50 });
}
return {
data: jpegBuffer.toString("base64"),
mimeType: "image/jpeg",
};
}
/**
* Get original image as base64 PNG (no compression)
*/
export function toBase64Png(buffer: Buffer): { data: string; mimeType: string } {
return {
data: buffer.toString("base64"),
mimeType: "image/png",
};
}
