Add warning to suppress png scaling warning

Close #120

lib/squib/card.rb

@@ -42,7 +42,6 @@ module Squib
       end
     end
 
-
   # A save/restore wrapper for using Cairo
   # :nodoc:
   # @api private

lib/squib/conf.rb

@@ -26,6 +26,7 @@ module Squib
       'smart_quotes'  => true,
       'text_hint'     => 'off',
       'warn_ellipsize'=> true,
+      'warn_png_scale'=> true,
     }
 
     #Translate the hints to the methods.
@@ -108,6 +109,10 @@ module Squib
       @config_hash['warn_ellipsize']
     end
 
+    def warn_png_scale?
+      @config_hash['warn_png_scale']
+    end
+
     private
 
     def normalize_antialias

lib/squib/graphics/image.rb

@@ -20,12 +20,15 @@ module Squib
       png = Squib.cache_load_image(file)
       use_cairo do |cc|
         cc.translate(box.x, box.y)
-        Squib.logger.warn "PNG scaling results in aliasing." if box.width != :native || box.height != :native
-        box.width  = png.width.to_f  if box.width  == :native
-        box.height = png.height.to_f if box.height == :native
-        box.width  = png.width.to_f * box.height.to_f / png.height.to_f if box.width == :scale
-        box.height = png.height.to_f * box.width.to_f / png.width.to_f  if box.height == :scale
-        cc.scale(box.width.to_f / png.width.to_f, box.height.to_f / png.height.to_f)
+        box.width    = png.width.to_f  if box.width  == :native
+        box.height   = png.height.to_f if box.height == :native
+        box.width    = png.width.to_f * box.height.to_f / png.height.to_f if box.width == :scale
+        box.height   = png.height.to_f * box.width.to_f / png.width.to_f  if box.height == :scale
+
+        scale_width  = box.width.to_f / png.width.to_f
+        scale_height = box.height.to_f / png.height.to_f
+        warn_png_scale(file, scale_width, scale_height)
+        cc.scale(scale_width, scale_height)
 
         cc.rotate(trans.angle)
         cc.flip(trans.flip_vertical, trans.flip_horizontal, box.width / 2, box.height / 2)
@@ -49,6 +52,14 @@ module Squib
       end
     end
 
+    # :nodoc:
+    # @api private
+    def warn_png_scale(file, scale_width, scale_height)
+      if @deck.conf.warn_png_scale? && (scale_width > 1.0 || scale_height > 1.0)
+        Squib.logger.warn "PNG is being upscaled - antialiasing could result: #{file}"
+      end
+    end
+
     # :nodoc:
     # @api private
     def svg(file, svg_args, box, paint, trans)

lib/squib/project_template/config.yml

@@ -42,4 +42,8 @@
 # By default, Squib warns when a text box is ellipsized. This can get verbose
 # and can be turned off here
 # warn_ellipsize: true # default
-# warn_ellipsize: false # default
+# warn_ellipsize: false # turn off entirely
+
+# By default, Squib will warn if a PNG is being up-scaled.
+# warn_png_scale: true # default
+# warn_png_scale: false # turn off entirely