feat:优化图片生产质量，减少打印耗时

miniprogram/constants/colors.ts

@@ -149,6 +149,9 @@ export function getRandomUniqueNumberColors(count: number): string[] {
     return Array.from(selectedColors);
 }
 
+/** A4 打印导出尺寸：150 DPI，兼顾清晰度与文件体积/打印速度 */
+export const A4_EXPORT_SIZE_150DPI = { width: 1240, height: 1754 };
+
 export const PAPER_SIZE = {
     A4: {
         // width: 2480,

miniprogram/utils/saveImage.ts

@@ -1,8 +1,16 @@
+import { A4_EXPORT_SIZE_150DPI } from '../constants/colors';
+
+/**
+ * 导出为固定打印分辨率（A4 150 DPI），避免高 DPR 设备导出过大图导致打印慢、文件大
+ */
 const doSaveImage = (canvas: Canvas) => {
+    const { width: destWidth, height: destHeight } = A4_EXPORT_SIZE_150DPI;
     wx.canvasToTempFilePath({
-        canvas: canvas,
-        fileType: 'png',
-        quality: 1,
+        canvas,
+        fileType: 'jpg',
+        quality: 0.9,
+        destWidth,
+        destHeight,
         success: (res) => {
             wx.saveImageToPhotosAlbum({
                 filePath: res.tempFilePath,