From cf5a46c86c2894d290ce309b77cabd80128268c4 Mon Sep 17 00:00:00 2001
From: admtracksteel <admtracksteel@gmail.com>
Date: Mon, 8 Jun 2026 11:02:43 +0000
Subject: [PATCH] =?UTF-8?q?=F0=9F=8E=A8=20fix:=20Remo=C3=A7=C3=A3o=20real?=
 =?UTF-8?q?=20de=20fundo=20branco=20via=20Canvas=20API=20-=20transpar?=
 =?UTF-8?q?=C3=AAncia=20genu=C3=ADna=20nos=20stickers=20de=20cena?=
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Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 public/app.js | 98 +++++++++++++++++++++++++++++++++++++++------------
 1 file changed, 76 insertions(+), 22 deletions(-)

diff --git a/public/app.js b/public/app.js
index 2434ffe..5293338 100644
--- a/public/app.js
+++ b/public/app.js
@@ -7610,6 +7610,54 @@ document.addEventListener('DOMContentLoaded', () => {
   const sceneLayersItems = document.getElementById('sceneLayersItems');
 
   // Cria um item de camada de imagem direto no canvas (background ou sticker)
+  // Remoção de fundo branco via Canvas API — gera PNG com transparência real
+  async function removeWhiteBackground(imgUrl, threshold = 235) {
+    return new Promise((resolve) => {
+      const img = new Image();
+      img.crossOrigin = 'anonymous'; // necessário para getImageData funcionar
+      img.onload = () => {
+        const offscreen = document.createElement('canvas');
+        offscreen.width = img.naturalWidth;
+        offscreen.height = img.naturalHeight;
+        const ctx = offscreen.getContext('2d', { willReadFrequently: true });
+        ctx.drawImage(img, 0, 0);
+
+        const imageData = ctx.getImageData(0, 0, offscreen.width, offscreen.height);
+        const data = imageData.data;
+        // threshold: pixels com R,G,B >= threshold são considerados "fundos a remover"
+        // softRange: faixa de suavização para bordas anti-aliased
+        const softRange = 20;
+
+        for (let i = 0; i < data.length; i += 4) {
+          const r = data[i];
+          const g = data[i + 1];
+          const b = data[i + 2];
+
+          // Pega o mínimo dos canais (garante que só pixels "esbranquiçados" sejam afetados)
+          const minChannel = Math.min(r, g, b);
+
+          if (minChannel >= threshold) {
+            // Área central do branco: totalmente transparente
+            data[i + 3] = 0;
+          } else if (minChannel >= threshold - softRange) {
+            // Zona de borda: transição linear suave para preservar contornos
+            const ratio = (minChannel - (threshold - softRange)) / softRange;
+            data[i + 3] = Math.round((1 - ratio) * data[i + 3]);
+          }
+          // Pixels abaixo do threshold - softRange: mantém opacidade original
+        }
+
+        ctx.putImageData(imageData, 0, 0);
+        resolve(offscreen.toDataURL('image/png'));
+      };
+      img.onerror = () => {
+        console.warn('[removeWhiteBackground] Falha ao carregar imagem, usando original:', imgUrl);
+        resolve(imgUrl);
+      };
+      img.src = imgUrl;
+    });
+  }
+
   function addSceneLayerToCanvas(layerData) {
     if (!canvasModeActive || !cartazPrintableArea) return;
 
@@ -7622,44 +7670,50 @@ document.addEventListener('DOMContentLoaded', () => {
     item.style.top = (layerData.top || 10) + '%';
     item.style.width = (layerData.width || 35) + '%';
     item.style.height = (layerData.height || 35) + '%';
-    item.style.zIndex = layerData.isBackground ? '1' : String(10 + (layerData.zOffset || 0));
+    item.style.zIndex = layerData.isBackground ? '0' : String(10 + (layerData.zOffset || 0));
     item.style.background = 'transparent';
 
     if (layerData.isBackground) {
-      // Fundo: cobrindo 100% do canvas
       item.style.left = '0';
       item.style.top = '0';
       item.style.width = '100%';
       item.style.height = '100%';
       item.style.zIndex = '0';
-      item.style.isolation = 'isolate'; // Isola o fundo para evitar bleeding do blend-mode dos filhos
       item.style.pointerEvents = 'none';
       item.innerHTML = `<img src="${layerData.url}" 
         style="width:100%; height:100%; object-fit:cover; pointer-events:none; display:block;">`;
       item.title = '🖼️ Cenário de Fundo';
-    } else {
-      // Elementos: mix-blend-mode: multiply faz o fundo branco desaparecer (efeito sticker)
-      item.style.isolation = 'isolate';
-      item.innerHTML = `<img src="${layerData.url}" 
-        style="width:100%; height:100%; object-fit:contain; pointer-events:none;
-               mix-blend-mode: multiply; display:block;">`;
-      item.title = '🎬 ' + (layerData.name || 'Elemento');
-    }
 
-    const handle = document.createElement('div');
-    handle.className = 'canvas-resize-handle';
-    item.appendChild(handle);
-
-    cartazPrintableArea.appendChild(item);
-
-    if (!layerData.isBackground) {
-      setupCanvasItemEvents(item);
-      // Permitir que o fundo seja selecionável após clicar nele diretamente
-    } else {
-      // para o fundo, adicionar capacidade de clicar para habilitar arrastar
+      const handle = document.createElement('div');
+      handle.className = 'canvas-resize-handle';
+      item.appendChild(handle);
+      cartazPrintableArea.appendChild(item);
       item.style.pointerEvents = 'auto';
       setupCanvasItemEvents(item);
+
+    } else {
+      // Adiciona o item ao canvas com um placeholder de loading
+      item.innerHTML = `<div style="width:100%;height:100%;display:flex;align-items:center;justify-content:center;opacity:0.4;">
+        <span style="font-size:1.5rem;animation:spin 1s linear infinite;">⏳</span>
+      </div>`;
+      item.title = '🎬 ' + (layerData.name || 'Elemento');
+
+      const handle = document.createElement('div');
+      handle.className = 'canvas-resize-handle';
+      item.appendChild(handle);
+      cartazPrintableArea.appendChild(item);
+      setupCanvasItemEvents(item);
+
+      // Remove o fundo branco de forma assíncrona via Canvas API
+      removeWhiteBackground(layerData.url).then(transparentDataUrl => {
+        item.innerHTML = `<img src="${transparentDataUrl}" 
+          style="width:100%; height:100%; object-fit:contain; pointer-events:none; display:block;">`;
+        const newHandle = document.createElement('div');
+        newHandle.className = 'canvas-resize-handle';
+        item.appendChild(newHandle);
+      });
     }
+
     return item;
   }