PNG/SVG: flipping is now supported.

Fixes #11

lib/squib/api/image.rb

@@ -32,6 +32,8 @@ module Squib
     # @option opts crop_corner_y_radius [Integer] (0): y radius for rounded corners of cropped image. Supports Unit Conversion, see {file:README.md#Units Units}.
     # @option opts crop_width [Integer] (:native): Width of the cropped image. Supports Unit Conversion, see {file:README.md#Units Units}.
     # @option opts crop_height [Integer] (:native): Height of the cropped image. Supports Unit Conversion, see {file:README.md#Units Units}.
+    # @option opts flip_horiztonal [Boolean] (false): Flip this image about its center horizontally (i.e. left becomes right and vice versa).
+    # @option opts flip_vertical [Boolean] (false): Flip this image about its center verticall (i.e. top becomes bottom and vice versa).
     # @return [nil] Returns nil
     # @api public
     def png(opts = {})
@@ -79,6 +81,8 @@ module Squib
     # @option opts crop_corner_y_radius [Integer] (0): y radius for rounded corners of cropped image. Supports Unit Conversion, see {file:README.md#Units Units}.
     # @option opts crop_width [Integer] (:native): Width of the cropped image. Supports Unit Conversion, see {file:README.md#Units Units}.
     # @option opts crop_height [Integer] (:native): Height of the cropped image. Supports Unit Conversion, see {file:README.md#Units Units}.
+    # @option opts flip_horiztonal [Boolean] (false): Flip this image about its center horizontally (i.e. left becomes right and vice versa).
+    # @option opts flip_vertical [Boolean] (false): Flip this image about its center verticall (i.e. top becomes bottom and vice versa).
     # @return [nil] Returns nil
     # @api public
     def svg(opts = {})

lib/squib/args/transform.rb

@@ -20,6 +20,8 @@ module Squib
           crop_corner_radius: nil,
           crop_corner_x_radius: 0,
           crop_corner_y_radius: 0,
+          flip_vertical: false,
+          flip_horizontal: false,
         }
       end
 
@@ -28,7 +30,7 @@ module Squib
       end
 
       def self.params_with_units
-        parameters.keys # all of them
+        parameters.keys - [:flip_vertical, :flip_horizontal]
       end
 
       def validate_crop_width(arg, _i)

lib/squib/graphics/cairo_context_wrapper.rb

@@ -94,6 +94,18 @@ module Squib
         translate(-x, -y)
       end
 
+      # Flip either vertical or horizontal depending
+      # From the cairo website: http://cairographics.org/matrix_transform/
+      # cairo.Matrix(fx, 0,         0,
+      #              fy, cx*(1-fx), cy*(fy-1))
+      # fx/fy = 1 means 'no flip', fx/fy = -1 are used for horizontal/vertical flip
+      def flip(vertical, horizontal, x, y)
+        v = vertical   ? -1.0 : 1.0
+        h = horizontal ? -1.0 : 1.0
+        transform Cairo::Matrix.new(v, 0.0,     0.0,
+                                    h, x*(1-v), y*(1-h))
+      end
+
     end
   end
 end

lib/squib/graphics/image.rb

@@ -20,15 +20,15 @@ module Squib
       png = Squib.cache_load_image(file)
       use_cairo do |cc|
         cc.translate(box.x, box.y)
-        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
-          Squib.logger.warn "PNG scaling results in aliasing."
-          cc.scale(box.width.to_f / png.width.to_f, box.height.to_f / png.height.to_f)
-        end
+        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)
+
         cc.rotate(trans.angle)
+        cc.flip(trans.flip_vertical, trans.flip_horizontal, box.width / 2, box.height / 2)
         cc.translate(-box.x, -box.y)
 
         trans.crop_width  = png.width.to_f  if trans.crop_width  == :native
@@ -37,6 +37,7 @@ module Squib
         cc.clip
         cc.translate(-trans.crop_x, -trans.crop_y)
 
+
         cc.set_source(png, box.x, box.y)
         cc.operator = paint.blend unless paint.blend == :none
         if paint.mask.empty?
@@ -64,6 +65,7 @@ module Squib
       scale_height = box.height.to_f / svg.height.to_f
       use_cairo do |cc|
         cc.translate(box.x, box.y)
+        cc.flip(trans.flip_vertical, trans.flip_horizontal, box.width / 2, box.height / 2)
         cc.rotate(trans.angle)
         cc.scale(scale_width, scale_height)