ImageExprParse.h

Classes

ImageExprParse -- Class to hold values from image expression parser (full description)

class ImageExprParse

Interface

Public Members
static LatticeExprNode command (const String& str)
static LatticeExprNode command (const String& str, const Block<LatticeExprNode>& tempLattices, const PtrBlock<const ImageRegion*>& tempRegions)
ImageExprParse (Bool value)
ImageExprParse (Int value)
ImageExprParse (Float value)
ImageExprParse (Double value)
ImageExprParse (const Complex& value)
ImageExprParse (const DComplex& value)
ImageExprParse (const Char* value)
ImageExprParse (const String& value)
LatticeExprNode makeFuncNode () const
LatticeExprNode makeFuncNode (const LatticeExprNode& arg1) const
LatticeExprNode makeFuncNode (const LatticeExprNode& arg1, const LatticeExprNode& arg2) const
LatticeExprNode makeFuncNode (const LatticeExprNode& arg1, const LatticeExprNode& arg2, const LatticeExprNode& arg3) const
LatticeExprNode makeLRNode() const
LatticeExprNode makeLitLRNode() const
LatticeExprNode makeRegionNode() const
LatticeExprNode makeLiteralNode() const
static Slice* makeSlice (const ImageExprParse& start)
static Slice* makeSlice (const ImageExprParse& start, const ImageExprParse& end)
static Slice* makeSlice (const ImageExprParse& start, const ImageExprParse& end, const ImageExprParse& incr)
static LatticeExprNode makeIndexinNode (const LatticeExprNode& axis, const vector<Slice>& slices)
static LatticeExprNode makeValueList (const Block<LatticeExprNode>& values)
static IPosition makeBinning (const LatticeExprNode& values)
static void setNode (const LatticeExprNode& node)
static void addNode (LatticeExprNode* node)
static void addNode (ImageExprParse* node)
static void deleteNodes()
Bool tryLatticeNode (LatticeExprNode& node, const String& name) const
LatticeExprNode makeImageNode (const String& name, const String& mask) const
static Table& getRegionTable (void*, Bool)

Description

Prerequisite

Etymology

ImageExprParse is the class used to parse an image expression command.

Synopsis

ImageExprParse is used by the parser of image expression statements. The parser is written in Bison and Flex in files ImageExprGram.y and .l. The statements in there use the routines in this file to act upon a reduced rule.

The main function (and the only function to be used by a user) is the static function ImageExprParse::command which parses an expression command. It returns a LatticeExprNode object containing the expression represented as a tree. The object can be used as a Lattice(Expr)<T> in other operations.

The syntax of the command is similar to that of expressions in C++. E.g.

   min(img1, img2) + sin(img3)
The following items can be used in an expression: When the expression is parsed, it is checked if the images and lattices involved have conforming shapes and coordinates. Note, however, that some functions (e.g. mean) reduce an image to a scalar. Such an image can have a different shape and coordinates.

The data types of the images and constants involved can be different. The data type of a subexpression is the common data type (e.g. Float and Double result in Double; Complex and Double result in DComplex). Automatic implicit conversions are done where needed. However, for performance reasons it may sometimes be better to convert explicitly. See below in the first example.

The expression evaluator (which is not part of the parser) evaluates the expression in chunks to avoid having to keep large temporary results. A scalar subexpression is evaluated only once to avoid unnecessary (possibly expensive) calculations.

Some examples:

img1 + min(float(pi()), mean(img2))
Suppose img1 and img2 are images with single precision data. They do not need to have conforming shapes and coordinates, because only the mean of img2 is used.
Note that pi is explicitly converted to single precision, because pi() results in a Double. If that was not done, the expression result would be a Double with the effect that all data of img1 had to be converted to Double.
min(img1, (min(img1)+max(img1))/2)
This example shows that there are 2 min functions. One with a single argument returning the minimum value of that image. The other with 2 arguments returning a lattice containing img1 data clipped at the value of the 2nd argument.

Example

    LatticeExpr<Double> expr ("a + sin(b)");
    ArrayLattice<Double> arr(expr.shape());
    arr.copyData (expr);
Line 1 creates a LatticeExpr object for the given expression. Note that a and b are names of lattice files (e.g. PagedImage).
Line 2 creates an ArrayLattice with the same shape as the expression (which is the shape of lattice a (and b)).
Line 3 copies the result of the expression to the ArrayLattice.

Motivation

It is necessary to be able to give an image expression command in ASCII. This can be used in glish to operate on lattices/images.

Member Description

static LatticeExprNode command (const String& str)
static LatticeExprNode command (const String& str, const Block<LatticeExprNode>& tempLattices, const PtrBlock<const ImageRegion*>& tempRegions)

Parse the given command. It will open all lattices needed. It returns the resulting image expression.
The tempLattices/tempRegions arguments make it possible to use temporary lattices/images and regions in the expression by means of the $n notation.

ImageExprParse (Bool value)
ImageExprParse (Int value)
ImageExprParse (Float value)
ImageExprParse (Double value)
ImageExprParse (const Complex& value)
ImageExprParse (const DComplex& value)
ImageExprParse (const Char* value)
ImageExprParse (const String& value)

Construct a literal object for the given type.

LatticeExprNode makeFuncNode () const
LatticeExprNode makeFuncNode (const LatticeExprNode& arg1) const
LatticeExprNode makeFuncNode (const LatticeExprNode& arg1, const LatticeExprNode& arg2) const
LatticeExprNode makeFuncNode (const LatticeExprNode& arg1, const LatticeExprNode& arg2, const LatticeExprNode& arg3) const

Make a LatticeExprNode for a function.

LatticeExprNode makeLRNode() const

Make a LatticeExprNode object for the lattice or region name.

LatticeExprNode makeLitLRNode() const

Make a LatticeExprNode object for the name of constant, lattice, or region.

LatticeExprNode makeRegionNode() const

Make a LatticeExprNode object for the temporary region number.

LatticeExprNode makeLiteralNode() const

Make a LatticeExprNode object for the literal value.

static Slice* makeSlice (const ImageExprParse& start)
static Slice* makeSlice (const ImageExprParse& start, const ImageExprParse& end)
static Slice* makeSlice (const ImageExprParse& start, const ImageExprParse& end, const ImageExprParse& incr)

Make a Slice object from 1-3 literals.

static LatticeExprNode makeIndexinNode (const LatticeExprNode& axis, const vector<Slice>& slices)

Make a node for the INDEXIN function.

static LatticeExprNode makeValueList (const Block<LatticeExprNode>& values)

Make an array from a value list.

static IPosition makeBinning (const LatticeExprNode& values)

Make an IPosition containing the binning values.

static void setNode (const LatticeExprNode& node)

Set the static node object (used by the .y file).

static void addNode (LatticeExprNode* node)
static void addNode (ImageExprParse* node)
static void deleteNodes()

Keep track of the nodes allocated while parsing the expression.

Bool tryLatticeNode (LatticeExprNode& node, const String& name) const

private: Try if the name represent a lattice or image. Return False if not.

LatticeExprNode makeImageNode (const String& name, const String& mask) const

Make the node from the image name and a mask name. The mask name can be NOMASK (case insensitive) meaning that no mask is applied to the image.

static Table& getRegionTable (void*, Bool)

Callback function for RegionHandlerTable to get the table to be used.