Generate by default indexed 8bpp tiff image.

This is the expected parameter to allow tesseract convertion.

product/PortalTransforms/libtransforms/imagemagick_transform.py

@@ -22,6 +22,9 @@ class ImageMagickTransforms:
             parameter_list.extend(['-resize', '%sx%s!' % (newwidth, newheight)])
         elif newwidth or newheight:
             parameter_list.extend(['-resize', '%sx%s' % (newwidth, newheight)])
+        depth = kwargs.get('depth','')
+        if depth:
+            parameter_list.extend(['-depth', '%s' % depth, '-type', 'Palette'])
         parameter_list.append('%s:-' % self.format)
         process = subprocess.Popen(parameter_list,
                                    stdin=subprocess.PIPE,

product/PortalTransforms/transforms/image_to_tiff.py

@@ -6,6 +6,9 @@ class image_to_tiff(ImageMagickTransforms):
     output   = 'image/tiff'
     format  = 'tiff'
 
+    def convert(self, orig, data, depth=8, **kwargs):
+        return ImageMagickTransforms.convert(self, orig, data, depth=depth, **kwargs)
+
 
 def register():
     return image_to_tiff()