When you create an image in Rmagick and save it, chances are high that your image will be way too big. The reason is that, by default, Rmagick creates uncompressed images.
Try to run
optipng <filename> for PNG or
jpegoptim --strip-all <filename> for JPG on your file, and you will probably see a file size reduction of 20% - 90%. That is without loosing image quality!
One way to improve on this is to set the compression level in Rmagick's write method. Here is some clunky code to do this:
compression = case image_file_name when /(jpg)|(jpeg)$/i Magick::LosslessJPEGCompression when /png$/i Magick::ZipCompression else nil end image.write(output_file_name) do self.compression = compression if compression end
The results are not as good as with the command line tools, but definitely better than uncompressed images. If your images are part of a web page, then you can reduce your page load time by reducing image size. To me this was a big deal on my current project.