class ProductImage < ApplicationRecord
  has_attached_file :picture, 
                    styles: { 
                      thumb: "64x64#", 
                      small: "100x100#", 
                      med: "150x150>", 
                      large: "200x200>" 
                    },
                    convert_options: {
                      thumb: '-quality 85',
                      small: '-quality 85',
                      med: '-quality 85',
                      large: '-quality 85'
                  }
  validates_attachment_content_type :picture, content_type: /\Aimage\/.*\z/
  belongs_to :color
end

class ProductImage < ApplicationRecord
  has_attached_file :picture, 
                    styles: { 
                      thumb: "64x64#", 
                      small: "100x100#", 
                      med: "150x150>", 
                      large: "200x200>" 
                    }
  validates_attachment_content_type :picture, content_type: /\Aimage\/.*\z/
  belongs_to :color
end

--- 
+++ 
@@ -5,7 +5,13 @@
                       small: "100x100#", 
                       med: "150x150>", 
                       large: "200x200>" 
-                    }
+                    },
+                    convert_options: {
+                      thumb: '-quality 85',
+                      small: '-quality 85',
+                      med: '-quality 85',
+                      large: '-quality 85'
+                  }
   validates_attachment_content_type :picture, content_type: /\Aimage\/.*\z/
   belongs_to :color
 end
Update on Image Conversion Attachement
