Pennysmalls

We have a nice new server which runs 64 bit fedora linux. It’s quick and good. But alas FreeImage won’t compile on this architecture. So bang goes any chance of using Image science.

But really I am only interested in finding the dimensions of my images. And it shouldn’t be hard. I found this post about using the gd library to resize images. Well I don’t need to resize images, but I thought it was a good approach, so I hacked it to do what I wanted.

Here is my code (credit to Damien Tanner for the original code). Very short and simple, and you just need the gd library installed together with the header files. On my system ‘yum install gd-devel’ did the trick.

if !ENV['HOME']
  ENV['INLINEDIR'] = RAILS_ROOT + "/tmp"
end

require 'inline'

class ImageInfo
  SUPPORTED_FORMATS = %w(jpg jpeg png gif)

  def initialize(filename, type=nil)
    @filename = filename
    @type = SUPPORTED_FORMATS.index(type || @filename[/[^\.]*$/].downcase)
  end

  def height
    unless @height
      image_size
    end
    @height
  end

  def width
    unless @width
      image_size
    end
    @width
  end

  def fetch_image_size(filename, image_type); end

  def image_size
    if @type
      fetch_image_size(@filename, @type)
    else
      raise "Unknown type of image"
    end
  end

  inline do |builder|
    builder.include '"gd.h"'
    builder.add_link_flags "-lgd"

    builder.c <<-"END"
    void fetch_image_size(char *filename, int image_type) {
      gdImagePtr im_in;
      FILE *in;

      in = fopen(filename, "rb");
      /* Support diff image types: jpg jpeg png gif */
      switch(image_type) {
        case 0:
        case 1: im_in = gdImageCreateFromJpeg(in);
            break;
        case 2: im_in = gdImageCreateFromPng(in);
            break;
        case 3: im_in = gdImageCreateFromGif(in);
            break;
      }
      fclose(in);
      if (im_in) {
        rb_iv_set(self, "@width", INT2FIX(im_in->sx));
        rb_iv_set(self, "@height", INT2FIX(im_in->sy));
      }
    }
    END
  end
end

To use it, do something like this:

begin
  iinfo = ImageInfo.new(filepath)
  my_image_width = iinfo.width
  my_image_height = iinfo.height
rescue Exception=>e
  # check errors
end