From f78a64d5455ac53a4621cd3c128ea5fbd27daea0 Mon Sep 17 00:00:00 2001
From: Felix Kaspar <ich@felixkaspar.com>
Date: Tue, 24 Oct 2023 19:31:14 +0200
Subject: [PATCH] Remove blank pages done, Updated README.md

---
 README.md                            |  2 +-
 public/functions/removeBlankPages.js | 52 +++++++++++++++++-----------
 2 files changed, 33 insertions(+), 21 deletions(-)

diff --git a/README.md b/README.md
index 6ad5dae6..47aa7aac 100644
--- a/README.md
+++ b/README.md
@@ -105,7 +105,7 @@ Current functions of spdf and their progress in this repo.
 
 | Status | Feature            | Description |
 | ------ | ------------------ | ----------- |
-| 🚧    | Remove Blank Pages |             |
+| ✔️    | Remove Blank Pages |             |
 | 🚧    | Auto Split Pages   |             |
 
 | Status | Feature      | Description |
diff --git a/public/functions/removeBlankPages.js b/public/functions/removeBlankPages.js
index a7a9c729..7e9fb939 100644
--- a/public/functions/removeBlankPages.js
+++ b/public/functions/removeBlankPages.js
@@ -1,30 +1,42 @@
 export async function removeBlankPages(snapshot, whiteThreashold, PDFJS, OpenCV, PDFLib) {
     
-    const pdfDoc = await PDFJS.getDocument(snapshot).promise;
+    const emptyPages = await findEmptyPages(snapshot);
 
-    const emptyPages = [];
-    for (let i = 1; i <= pdfDoc.numPages; i++) {
-        const page = await pdfDoc.getPage(i);
-        console.log("Checking images");
+    console.log("Empty Pages: ", emptyPages);
 
-        if(!await hasText(page)) {
-            console.log("Found text on Page, page is not empty");
-            continue;
+    const pdfDoc = await PDFLib.PDFDocument.load(snapshot);
+
+    // Reverse the array before looping in order to keep the indecies at the right pages. E.g. if you delete page 5 page 7 becomes page 6, if you delete page 7 page 5 remains page 5
+    emptyPages.reverse().forEach(pageIndex => {
+        pdfDoc.removePage(pageIndex);
+    })
+
+    return pdfDoc.save();
+
+    async function findEmptyPages(snapshot) {
+        const pdfDoc = await PDFJS.getDocument(snapshot).promise;
+
+        const emptyPages = [];
+        for (let i = 1; i <= pdfDoc.numPages; i++) {
+            const page = await pdfDoc.getPage(i);
+            console.log("Checking page " + i);
+    
+            if(!await hasText(page)) {
+                console.log(`Found text on Page ${i}, page is not empty`);
+                continue;
+            }
+    
+            if(!await areImagesBlank(page, whiteThreashold)) {
+                console.log(`Found non white image on Page ${i}, page is not empty`);
+                continue;
+            }
+    
+            console.log(`Page ${i} is empty.`);
+            emptyPages.push(i - 1);
         }
-
-        if(!await areImagesBlank(page, whiteThreashold)) {
-            console.log("Found image on Page, page is not empty");
-            continue;
-        }
-
-        emptyPages.push[i];
+        return emptyPages;
     }
 
-    console.log(emptyPages);
-
-    // TODO: Remove emptyPages using pdflib
-    // return pdf;
-
     async function areImagesBlank(page, whiteThreashold) {
         const ops = await page.getOperatorList();