Class: ImageInspector::Image

Inherits:
Object
  • Object
show all
Defined in:
lib/imageinspector.rb

Overview

Parse image header and retrieve its basic properties. The code is inspired by Sam Stephenson’s snippet which demonstrates how to determine a JPEG image size ( see snippets.dzone.com/posts/show/805) and Paul Schreiber’s code for TIFF (see paulschreiber.com/blog/2010/06/10/tiff-file-dimensions-in-ruby/)

Supported formats are: TIFF, PNG, JPEG and JPEG2000.

Constant Summary collapse

@@gc = 
(IO.method_defined? :getbyte) ? (:getbyte) : (:getc)

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(input = nil) ⇒ Image

Set all image attributes to nil and open an image if an optional argument is specified.



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# File 'lib/imageinspector.rb', line 77

def initialize( input=nil )
  clearData()
  open( input ) unless input.nil?
end

Instance Attribute Details

#compression ⇒ Object (readonly)

Image format and compression method



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# File 'lib/imageinspector.rb', line 68

def compression
  @compression
end

#cspace ⇒ Object (readonly)

Image depth, color space, palette (for indexed images) and transparency data (for PNG)



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# File 'lib/imageinspector.rb', line 66

def cspace
  @cspace
end

#depth ⇒ Object (readonly)

Image depth, color space, palette (for indexed images) and transparency data (for PNG)



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# File 'lib/imageinspector.rb', line 66

def depth
  @depth
end

#format ⇒ Object (readonly)

Image format and compression method



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# File 'lib/imageinspector.rb', line 68

def format
  @format
end

#height ⇒ Object (readonly)

Return the obvious.



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# File 'lib/imageinspector.rb', line 61

def height
  @height
end

#palette ⇒ Object (readonly)

Image depth, color space, palette (for indexed images) and transparency data (for PNG)



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# File 'lib/imageinspector.rb', line 66

def palette
  @palette
end

#tags ⇒ Object (readonly)

Return TIFF tags as a hash for TIFF images or JPEG images with EXIF data. Otherwise this property is nil.



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# File 'lib/imageinspector.rb', line 71

def tags
  @tags
end

#trans ⇒ Object (readonly)

Image depth, color space, palette (for indexed images) and transparency data (for PNG)



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# File 'lib/imageinspector.rb', line 66

def trans
  @trans
end

#width ⇒ Object (readonly)

Return the obvious.



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# File 'lib/imageinspector.rb', line 61

def width
  @width
end

#x_dpi ⇒ Object (readonly)

Return image resolution (always in pixels per inch, even if it is differently specified in the source image).



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# File 'lib/imageinspector.rb', line 64

def x_dpi
  @x_dpi
end

#y_dpi ⇒ Object (readonly)

Return image resolution (always in pixels per inch, even if it is differently specified in the source image).



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# File 'lib/imageinspector.rb', line 64

def y_dpi
  @y_dpi
end

Instance Method Details

#getRawData ⇒ Object

Return image data (possibly compressed) for a previously initialized image as a sring. For JPEG and JPEG2000 this would be the whole image as it is stored on the disk, while for TIFF and PNG all headers are stripped and a raw data stream is returned.



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# File 'lib/imageinspector.rb', line 106

def getRawData()
  raise "The image has not been properly initialized" if @width.nil? or @input.nil?

  begin
    if @input.kind_of? IO or @input.kind_of? StringIO
      ret = concatDataBlocks( @input )
    else
      File.open( @input, 'rb' ) { |io| ret = concatDataBlocks( io ) }
    end
    return ret
  rescue Exception => e
    $stderr.puts( "Could not read data from #{@fname}: " << e.message )
  end
end

#nextImage ⇒ Object 



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# File 'lib/imageinspector.rb', line 121

def nextImage()
  if @format.eql? :TIFF and @next_off > 0
    begin
      if @input.kind_of? IO or @input.kind_of? StringIO
        tiffNext( @input )
      else
        File.open( @input, 'rb' ) { |io| tiffNext( io ) }
      end
      return true
    rescue Exception => e
      $stderr.puts( "Could not read data from #{@fname}: " << e.message )
    end
  end
  false
end

#open(input) ⇒ Object

Accepts either a file name or a stream-like object.



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# File 'lib/imageinspector.rb', line 83

def open( input )
  @input = input

  begin
    if input.kind_of? IO or input.kind_of? StringIO
      @fname = '<STREAM>'
      byFormat( input )
    else
      @fname = input
      File.open( input, 'rb' ) { |io| byFormat( io ) }
    end

  rescue Exception => e
    $stderr.puts( "Could not read data from #{@fname}: " << e.message )
    clearData()
    @input = nil
  end
end