replace image src with "lazy loaded" src only if the latter exists

lib/single-file/single-file-core.js

@@ -82,9 +82,6 @@ const SingleFileCore = (() => {
 			if (!this.options.jsEnabled || (this.options.saveRawPage && this.options.removeScripts)) {
 				this.processor.insertNoscriptContents();
 			}
-			if (this.options.lazyLoadImages) {
-				this.processor.lazyLoadImages();
-			}
 			if (this.options.removeFrames) {
 				this.processor.removeFrames();
 			}
@@ -145,6 +142,9 @@ const SingleFileCore = (() => {
 					}
 				});
 			await this.pendingPromises;
+			if (this.options.lazyLoadImages) {
+				this.processor.lazyLoadImages();
+			}
 			if (this.options.removeUnusedCSSRules) {
 				this.processor.removeUnusedCSSRules();
 			}
@@ -281,19 +281,19 @@ const SingleFileCore = (() => {
 
 		lazyLoadImages() {
 			this.doc.querySelectorAll("img[data-src]").forEach(imgElement => {
-				if (imgElement.dataset.src && imgElement.src != imgElement.dataset.src) {
+				if (imgElement.dataset.src && imgElement.dataset.src.startsWith(DATA_URI_PREFIX) && imgElement.src != imgElement.dataset.src) {
 					imgElement.src = imgElement.dataset.src;
 					imgElement.removeAttribute("data-src");
 				}
 			});
 			this.doc.querySelectorAll("img[data-original]").forEach(imgElement => {
-				if (imgElement.dataset.original && imgElement.src != imgElement.dataset.original) {
+				if (imgElement.dataset.original && imgElement.dataset.original.startsWith(DATA_URI_PREFIX) && imgElement.src != imgElement.dataset.original) {
 					imgElement.src = imgElement.dataset.original;
 					imgElement.removeAttribute("data-original");
 				}
 			});
 			this.doc.querySelectorAll("[data-bg]").forEach(element => {
-				if (element.dataset.bg && !element.style.backgroundImage.includes(element.dataset.bg)) {
+				if (element.dataset.bg && element.dataset.bg.startsWith(DATA_URI_PREFIX) && !element.style.backgroundImage.includes(element.dataset.bg)) {
 					element.style.backgroundImage = "url(" + element.dataset.bg + ")";
 					element.removeAttribute("data-bg");
 				}
@@ -448,14 +448,19 @@ const SingleFileCore = (() => {
 		}
 
 		async pageResources() {
-			await Promise.all([
+			const resourcePromises = [
 				DomProcessorHelper.processAttribute(this.doc.querySelectorAll("link[href][rel*=\"icon\"]"), "href", this.baseURI),
 				DomProcessorHelper.processAttribute(this.doc.querySelectorAll("img[src], input[src][type=image], object[type=\"image/svg+xml\"], object[type=\"image/svg-xml\"], embed[src*=\".svg\"]"), "src", this.baseURI),
 				DomProcessorHelper.processAttribute(this.doc.querySelectorAll("video[poster]"), "poster", this.baseURI),
 				DomProcessorHelper.processAttribute(this.doc.querySelectorAll("*[background]"), "background", this.baseURI),
 				DomProcessorHelper.processAttribute(this.doc.querySelectorAll("image, use"), "xlink:href", this.baseURI),
 				DomProcessorHelper.processSrcset(this.doc.querySelectorAll("[srcset]"), this.baseURI, this.dom)
-			]);
+			];
+			if (this.options.lazyLoadImages) {
+				resourcePromises.push(this.doc.querySelectorAll("img[data-src], img[data-original], [data-bg]"));
+				resourcePromises.push(DomProcessorHelper.processSrcset(this.doc.querySelectorAll("[data-srcset]"), this.baseURI, this.dom));
+			}
+			await resourcePromises;
 		}
 
 		async inlineStylesheets(initialization) {