remove alpha channel from png: issue #1914

Author: zdenop

src/api/baseapi.cpp

@@ -611,6 +611,13 @@ void TessBaseAPI::SetSourceResolution(int ppi) {
  */
 void TessBaseAPI::SetImage(Pix* pix) {
   if (InternalSetImage()) {
+    if (pixGetSpp(pix) == 4 && pixGetInputFormat(pix) == IFF_PNG) {
+      // remove alpha channel from png
+      PIX* p1 = pixRemoveAlpha(pix);
+      pixSetSpp(p1, 3);
+      pix = pixCopy(nullptr, p1);
+      pixDestroy(&p1);
+	  }
     thresholder_->SetImage(pix);
     SetInputImage(thresholder_->GetPixRect());
   }

src/api/pdfrenderer.cpp

@@ -716,14 +716,7 @@ bool TessPDFRenderer::imageToPDFObj(Pix *pix,
   const int kJpegQuality = jpg_quality;
 
   int format, sad;
-  if (filename) {
-    findFileFormat(filename, &format);
-    if (pixGetSpp(pix) == 4 && format == IFF_PNG) {
-      Pix *p1 = pixAlphaBlendUniform(pix, 0xffffff00);
-      sad = pixGenerateCIData(p1, L_FLATE_ENCODE, 0, 0, &cid);
-      pixDestroy(&p1);
-    }
-  }
+  sad = pixGenerateCIData(pix, L_FLATE_ENCODE, 0, 0, &cid);
   if (!cid) {
     sad = l_generateCIDataForPdf(filename, pix, kJpegQuality, &cid);
   }