make convertImage more flexible

Author: silverwind

web_src/js/features/copycontent.js

@@ -1,6 +1,6 @@
 import {copyToClipboard} from './clipboard.js';
 import {showTemporaryTooltip} from '../modules/tippy.js';
-import {imageBlobToPng} from '../utils.js';
+import {convertImage} from '../utils.js';
 const {i18n} = window.config;
 
 async function doCopy(content, btn) {
@@ -47,7 +47,7 @@ export function initCopyContent() {
     } catch {
       if (isImage) { // convert image to png as last-resort as some browser only support png copy
         try {
-          await doCopy(await imageBlobToPng(content), btn);
+          await doCopy(await convertImage(content, 'image/png'), btn);
         } catch {
           showTemporaryTooltip(btn, i18n.copy_error);
         }

web_src/js/utils.js

@@ -104,8 +104,8 @@ export function blobToDataURI(blob) {
   });
 }
 
-// convert any image Blob to a png Blob
-export function imageBlobToPng(blob) {
+// convert image Blob to another mime-type format.
+export function convertImage(blob, mime) {
   return new Promise(async (resolve, reject) => {
     try {
       const img = new Image();
@@ -118,7 +118,7 @@ export function imageBlobToPng(blob) {
         canvas.toBlob((blob) => {
           if (!(blob instanceof Blob)) return reject(new Error('imageBlobToPng failed'));
           resolve(blob);
-        }, 'image/png');
+        }, mime);
       });
       img.addEventListener('error', () => {
         reject(new Error('imageBlobToPng failed'));