Perl Graphics Programming

Sizing and Transforming Images

A lot of image manipulation tasks consist of little more than resizing and cropping existing images. Table 3-3 shows the Image::Magick attributes that provide sizing and resolution information about an image. The page and density attributes may be set (with Set( )) to control the image size and resolution before reading in a PostScript file. The size attribute can be similarly set before creating images from raw data formats.

Table 3-3. Sizing and resolution attributes

Attribute	Read	Write	Description
base_columns	Yes	No	Returns an integer that is the width of the image before any transformations have been performed.
base_rows	Yes	No	Returns an integer that is the height of the image before any transformations have been performed.
columns	Yes	No	Returns the width (integer number of pixel columns) of the image.
Density	Yes	Yes	Use this attribute to set the vertical and horizontal resolution of an image. Set the density to a string in the form ‘horiz-density x vert-density’, e.g., ‘300x300’. It is most useful when reading a PostScript document. The default is 72 dots per inch. Increase this to 144, for example, to render the PostScript to a larger sized image.
Geometry	Yes	No	Returns the bounds of the image. The geometry string is a convenient form that allows you to specify the width and height, or a region of an image with an offset. For example: geometry=>'640x800' is equivalent to: width=>640, height=>800 To refer to a 20x20 region of pixels starting at coordinate (100,150), ...