122 lines
3.8 KiB
TypeScript
122 lines
3.8 KiB
TypeScript
import sharp from "sharp";
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/**
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* 解析大小字符串为字节数
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*/
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function parseSize(size: string): number {
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const match = size.toLowerCase().match(/^(\d+(?:\.\d+)?)\s*(kb|mb|gb|b)?$/);
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if (!match) {
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throw new Error(`无效的大小格式: ${size}`);
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}
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const value = parseFloat(match[1]);
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const unit = match[2] || "b";
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const multipliers: Record<string, number> = {
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b: 1,
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kb: 1024,
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mb: 1024 * 1024,
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gb: 1024 * 1024 * 1024,
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};
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return Math.floor(value * multipliers[unit]);
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}
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/**
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* 将base64字符串转换为Buffer
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*/
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function base64ToBuffer(base64: string): Buffer {
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const base64Data = base64.replace(/^data:image\/\w+;base64,/, "");
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return Buffer.from(base64Data, "base64");
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}
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/**
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* 压缩Buffer到指定大小以内
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*/
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async function compressToSize(imageBuffer: Buffer, maxBytes: number, originalWidth: number, originalHeight: number): Promise<Buffer> {
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let quality = 90;
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let scale = 1;
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while (true) {
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const targetWidth = Math.round(originalWidth * scale);
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const targetHeight = Math.round(originalHeight * scale);
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const resultBuffer = await sharp(imageBuffer).resize(targetWidth, targetHeight, { fit: "fill" }).jpeg({ quality }).toBuffer();
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if (resultBuffer.length <= maxBytes) {
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return resultBuffer;
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}
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if (quality > 10) {
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quality -= 10;
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} else {
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quality = 90;
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scale *= 0.8;
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}
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}
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}
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/**
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* 压缩单张图片到指定大小以内
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* @param imageBase64 - base64编码的图片
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* @param maxSize - 最大输出大小，支持格式如 "10mb", "5MB", "1024kb" 等
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* @returns 压缩后的图片base64字符串
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*/
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export async function compressImage(imageBase64: string, maxSize = "10mb"): Promise<string> {
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const maxBytes = parseSize(maxSize);
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const imageBuffer = base64ToBuffer(imageBase64);
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const metadata = await sharp(imageBuffer).metadata();
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const resultBuffer = await compressToSize(imageBuffer, maxBytes, metadata.width || 1, metadata.height || 1);
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return resultBuffer.toString("base64");
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}
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/**
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* 将多张图片横向拼接为一张，并确保输出大小不超过指定限制
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* @param imageBase64List - base64编码的图片数组
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* @param maxSize - 最大输出大小，支持格式如 "10mb", "5MB", "1024kb" 等
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* @returns 拼接后的图片base64字符串
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*/
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export async function mergeImages(imageBase64List: string[], maxSize = "10mb"): Promise<string> {
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if (imageBase64List.length === 0) {
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throw new Error("图片列表不能为空");
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}
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const maxBytes = parseSize(maxSize);
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const imageBuffers = imageBase64List.map(base64ToBuffer);
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const imageMetadatas = await Promise.all(imageBuffers.map((buffer) => sharp(buffer).metadata()));
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const maxHeight = Math.max(...imageMetadatas.map((m) => m.height || 0));
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// 计算各图片调整后的宽度
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const imageWidths = imageMetadatas.map((metadata) => {
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const aspectRatio = (metadata.width || 1) / (metadata.height || 1);
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return Math.round(maxHeight * aspectRatio);
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});
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const totalWidth = imageWidths.reduce((sum, w) => sum + w, 0);
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// 拼接图片
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const resizedImages = await Promise.all(
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imageBuffers.map(async (buffer, index) => {
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return sharp(buffer).resize(imageWidths[index], maxHeight, { fit: "cover" }).toBuffer();
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}),
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);
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let currentX = 0;
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const compositeInputs = resizedImages.map((buffer, index) => {
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const input = { input: buffer, left: currentX, top: 0 };
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currentX += imageWidths[index];
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return input;
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});
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const mergedBuffer = await sharp({
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create: {
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width: totalWidth,
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height: maxHeight,
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channels: 4,
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background: { r: 255, g: 255, b: 255, alpha: 1 },
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},
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})
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.composite(compositeInputs)
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.jpeg({ quality: 90 })
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.toBuffer();
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// 复用压缩逻辑
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const resultBuffer = await compressToSize(mergedBuffer, maxBytes, totalWidth, maxHeight);
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return resultBuffer.toString("base64");
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} |