X11 Geometry Specifications

X11 geometry specifications are in the form "<width>x<height>{+-}<xoffset>{+-}<yoffset>" (where width, height, xoffset, and yoffset are numbers) for specifying the size and placement location for an object.

The width and height parts of the geometry specification are measured in pixels. The xoffset and yoffset parts are also measured in pixels and are used to specify the distance of the placement coordinate from the left and top and edges of the image, respectively. Both types of offsets are measured from the indicated edge of the object to the corresponding edge of the image. The X offset may be specified in the following ways:

The Y offset has similar meanings:

Offsets must be given as pairs; in other words, in order to specify either xoffset or yoffset both must be present.

GraphicsMagick Extensions To X11 Geometry Specifications

GraphicsMagick has added a number of qualifiers to the standard geometry string for use when resizing images. The form of an extended geometry string is "<width>x<height>{+-}<xoffset>{+-}<yoffset>{%}{@}{!}{^}{<}{>}". Extended geometry strings should only be used when resizing an image. Using an extended geometry string for other applications may cause the API call to fail. The available qualifiers are shown in the following table:

Postscript Page Size Extension To Geometry Specifications

Any geometry string specification supplied to the Geometry constructor is considered to be a Postscript page size nickname if the first character is not numeric. The page size nickname is not case sensitive. The Geometry constructor converts these page size specifications into the equivalent numeric geometry string specification (preserving any offset component) prior to conversion to the internal object format. Postscript page size specifications are short-hand for the pixel geometry required to fill a page of that size. Since the 11x17 inch page size used in the US starts with a digit, it is not supported as a Postscript page size nickname. Instead, substitute the geometry specification "792x1224>" when 11x17 output is desired.

The following is the definition of the Magick::Geometry class:

class Geometry
{
public:

  Geometry ( unsigned int width_,
             unsigned int height_,
             unsigned int xOff_ = 0,
             unsigned int yOff_ = 0,
             bool xNegative_ = false,
             bool yNegative_ = false );
  Geometry ( const std::string &geometry_ );
  Geometry ( const char * geometry_ );
  Geometry ( const Geometry &geometry_ );
  Geometry ( );
  ~Geometry ( void );

  // Width
  void          width ( unsigned int width_ );
  unsigned int  width ( void ) const;

  // Height
  void          height ( unsigned int height_ );
  unsigned int  height ( void ) const;

  // X offset from origin
  void          xOff ( unsigned int xOff_ );
  unsigned int  xOff ( void ) const;

  // Y offset from origin
  void          yOff ( unsigned int yOff_ );
  unsigned int  yOff ( void ) const;

  // Sign of X offset negative? (X origin at right)
  void          xNegative ( bool xNegative_ );
  bool          xNegative ( void ) const;

  // Sign of Y offset negative? (Y origin at bottom)
  void          yNegative ( bool yNegative_ );
  bool          yNegative ( void ) const;

  // Width and height are expressed as percentages
  void          percent ( bool percent_ );
  bool          percent ( void ) const;

  // Resize without preserving aspect ratio (!)
  void          aspect ( bool aspect_ );
  bool          aspect ( void ) const;

  // Resize if image is greater than size (>)
  void          greater ( bool greater_ );
  bool          greater ( void ) const;

  // Resize if image is less than size (<)
  void          less ( bool less_ );
  bool          less ( void ) const;

  // Resize image to fit total pixel area specified by dimensions (@).
  void          limitPixels ( bool limitPixels_ );
  bool          limitPixels ( void ) const;

  // Dimensions are treated as minimum rather than maximum values (^)
  void          fillArea ( bool fillArea_ );
  bool          fillArea ( void ) const;

  // Does object contain valid geometry?
  void          isValid ( bool isValid_ );
  bool          isValid ( void ) const;

  // Set via geometry string
  const Geometry& operator = ( const std::string &geometry_ );
  const Geometry& operator = ( const char * geometry_ );

  // Assignment operator
  Geometry& operator= ( const Geometry& Geometry_ );

  // Return geometry string
  operator std::string() const;

};

Copyright © Bob Friesenhahn 1999 - 2022