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Object subclass:#DisplayTransform
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instanceVariableNames:''
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classVariableNames:''
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poolDictionaries:''
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category:'Graphics-Transformations'
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!
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DisplayTransform comment:'This class represents a base for generic transformations of 2D points between different coordinate systems (including scaling and rotation). The transformations map objects between one coordinate system and another where it is assumed that a nested hierarchy of transformations can be defined.
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It is assumed that transformations deal with Integer points. All transformations should return Integer coordinates (even though float points may be passed in as argument).
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Compositions of transformations MUST work in the following order. A ''global'' transformation (the argument in #composedWithGlobal:) is defined as a transformation that takes place between the receiver (the ''local'') transformation and any ''global'' point computations, whereas a ''local'' transformation (e.g., the argument in #composedWithLocal:) takes place between the receiver (''global'') and any ''local'' points. For the transformation methods this means that combining a global and a local transformation will result in the following order:
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globalPointToLocal: globalPoint
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"globalPoint -> globalTransform -> localTransform -> locaPoint"
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^localTransform globalPointToLocal:
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(globalTransform globalPointToLocal: globalPoint)
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localPointToGlobal: localPoint
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"localPoint -> localTransform -> globalTransform -> globalPoint"
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^globalTransform localPointToGlobal:
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(localTransform localPointToGlobal: localPoint)
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'!
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!DisplayTransform class methodsFor:'instance creation'!
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identity
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^self new setIdentity! !
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!DisplayTransform methodsFor:'accessing'!
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inverseTransformation
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"Return the inverse transformation of the receiver"
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^self subclassResponsibility! !
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!DisplayTransform methodsFor:'composing'!
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composedWithGlobal: aTransformation
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"Return the composition of the receiver and the global transformation passed in.
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A 'global' transformation is defined as a transformation that takes place
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between the receiver (the 'local') transformation and any 'global' point
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computations, e.g., for the methods
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globalPointToLocal: globalPoint
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globalPoint -> globalTransform -> localTransform -> locaPoint
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localPointToGlobal: localPoint
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localPoint -> localTransform -> globalTransform -> globalPoint
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"
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^aTransformation composedWithLocal: self!
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composedWithLocal: aTransformation
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"Return the composition of the receiver and the local transformation passed in.
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A 'local' transformation is defined as a transformation that takes place
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between the receiver (the 'global') transformation and any 'local' point
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computations, e.g., for the methods
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globalPointToLocal: globalPoint
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globalPoint -> globalTransform -> localTransform -> locaPoint
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localPointToGlobal: localPoint
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localPoint -> localTransform -> globalTransform -> globalPoint
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"
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self isIdentity ifTrue:[^ aTransformation].
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aTransformation isIdentity ifTrue:[^ self].
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^ CompositeTransform new globalTransform: self
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localTransform: aTransformation! !
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!DisplayTransform methodsFor:'converting'!
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asCompositeTransform
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"Represent the receiver as a composite transformation"
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^CompositeTransform new
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globalTransform: self
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localTransform: self species identity!
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asMatrixTransform2x3
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"Represent the receiver as a 2x3 matrix transformation"
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^self subclassResponsibility! !
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!DisplayTransform methodsFor:'initialize'!
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setIdentity
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"Initialize the receiver to the identity transformation (e.g., not affecting points)"
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^self subclassResponsibility! !
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!DisplayTransform methodsFor:'testing'!
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isCompositeTransform
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"Return true if the receiver is a composite transformation.
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Composite transformations may have impact on the accuracy."
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^false!
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isIdentity
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"Return true if the receiver is the identity transform; that is, if applying to a point returns the point itself."
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^self subclassResponsibility!
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isMatrixTransform2x3
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"Return true if the receiver is 2x3 matrix transformation"
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^false!
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isMorphicTransform
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"Return true if the receiver is a MorphicTransform, that is specifies the transformation values explicitly."
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^false!
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isPureTranslation
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"Return true if the receiver specifies no rotation or scaling."
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^self subclassResponsibility! !
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!DisplayTransform methodsFor:'transforming points'!
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globalPointToLocal: aPoint
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"Transform aPoint from global coordinates into local coordinates"
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^self subclassResponsibility!
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globalPointsToLocal: inArray
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"Transform all the points of inArray from global into local coordinates"
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^inArray collect:[:pt| self globalPointToLocal: pt]!
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localPointToGlobal: aPoint
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"Transform aPoint from local coordinates into global coordinates"
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^self subclassResponsibility!
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localPointsToGlobal: inArray
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"Transform all the points of inArray from local into global coordinates"
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^inArray collect:[:pt| self localPointToGlobal: pt]! !
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!DisplayTransform methodsFor:'transforming rects'!
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globalBoundsToLocal: aRectangle
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"Transform aRectangle from global coordinates into local coordinates"
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^Rectangle encompassing: (self globalPointsToLocal: aRectangle corners)!
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localBoundsToGlobal: aRectangle
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"Transform aRectangle from local coordinates into global coordinates"
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^Rectangle encompassing: (self localPointsToGlobal: aRectangle corners)! !
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!DisplayTransform class methodsFor:'documentation'!
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version
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^ '$Header: /cvs/stx/stx/libview2/DisplayTransform.st,v 1.1 1999-10-06 22:22:58 cg Exp $'
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! !
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