feat: prepare GoodBuddy 0.8.0

src/main/bounded-jpeg.ts

@@ -0,0 +1,58 @@
+export const MAX_BOUNDED_JPEG_BYTES = 220 * 1024
+export const BOUNDED_JPEG_QUALITIES = [60, 45, 30, 20, 10] as const
+
+type JpegImage = {
+  getSize(): { width: number; height: number }
+  resize(options: {
+    width: number
+    quality: 'good'
+  }): JpegImage
+  toJPEG(quality: number): Buffer
+}
+
+export function isValidJpeg(data: Buffer): boolean {
+  return (
+    data.byteLength >= 4 &&
+    data[0] === 0xff &&
+    data[1] === 0xd8 &&
+    data.at(-2) === 0xff &&
+    data.at(-1) === 0xd9
+  )
+}
+
+export function encodeBoundedJpeg(
+  image: JpegImage,
+  maximumBytes = MAX_BOUNDED_JPEG_BYTES
+): Buffer {
+  if (!Number.isSafeInteger(maximumBytes) || maximumBytes < 4) {
+    throw new Error('JPEG 大小限制无效')
+  }
+  const initialWidth = Math.max(1, image.getSize().width)
+  const widths = [
+    initialWidth,
+    1_600,
+    1_280,
+    960,
+    720
+  ].filter(
+    (width, index, values) =>
+      width <= initialWidth && values.indexOf(width) === index
+  )
+
+  for (const width of widths) {
+    const candidate =
+      width === initialWidth
+        ? image
+        : image.resize({ width, quality: 'good' })
+    for (const quality of BOUNDED_JPEG_QUALITIES) {
+      const data = candidate.toJPEG(quality)
+      if (!isValidJpeg(data)) {
+        throw new Error('JPEG 图片内容无效')
+      }
+      if (data.byteLength <= maximumBytes) {
+        return data
+      }
+    }
+  }
+  throw new Error('JPEG 图片压缩后仍然过大')
+}