Watermarking an image in Rails
Published: April 16th, 2007Need a guide on watermarking an image on Ruby on Rails? Well here’s a quick tip on how to do it!
In a recent task I had to add the ability to add watermarking support when a user uploads a photo. I thought this would be hard, but after some research and some coding, it came out to be rather easy. I got it down in four lines of code. First, as an attachment system, I used attachment_fu. For an image processor, I used RMagick. In my picture model:
def watermark_image dst = Magick::Image.read("#{RAILS_ROOT}/public/#{self.public_filename}").first src = Magick::Image.read("#{RAILS_ROOT}/config/upshot.png").first result = dst.composite(src, Magick::SouthEastGravity, Magick::OverCompositeOp) result.write("#{RAILS_ROOT}/public/#{self.public_filename}") end
Just plug that in, and call an after_safe on :watermark_image in the model. This is so that everytime a user uploads a photo, the watermark_image method is called.
I’m new to rails and attachment_fu can you post your model file code for this.
My model currently looks like this
class Asset :image,
:storage => :file_system,
:thumbnails => { :thumb_sm => [25,25],
:thumb_lg => [50,50],
:small => “150×150>”,
:medium => “300×300>”,
:large => “450×450>”
}
validates_as_attachment
def watermark_image
dst = Magick::Image.read(”#{RAILS_ROOT}/public/#{self.public_filename}”).first
src = Magick::Image.read(”#{RAILS_ROOT}/config/upshot.png”).first
result = dst.composite(src, Magick::SouthEastGravity, Magick::OverCompositeOp)
result.write(”#{RAILS_ROOT}/public/#{self.public_filename}”)
end
Where should i place the after_safe effent because i want all the generated images to have the watermark
It’s after_save in fact …
Cheers,
boris
(Please delete my previous post)
Put after_save :watermark_image at the top of your model file.
Example:
class Asset::image
after_save :watermark_image
:storage => :file_system
…blah blah blah, attachment_fu junk…
validates_as_attachment
def watermark_image
…watermark method…
end
end
Ready. Set. Go.
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