public PDFFunction(int theFunctionType,
    List theDomain,
    List theRange,
    StringBuffer theFunctionDataStream) 
{
        super();
        this.functionType = 4;    // dang well better be 4;
        this.functionDataStream = theFunctionDataStream;
        this.domain = theDomain;
        this.range = theRange;
}

create an complete Function object of Type 4, a postscript calculator function. Use null for an optional object parameter if you choose not to use it. For optional int parameters, pass the default.

Parameters:

theDomain - List object of Double objects. This is the domain of the function. See page 264 of the PDF 1.3 Spec.

theRange - List object of Double objects. This is the Range of the function. See page 264 of the PDF 1.3 Spec.

theFunctionDataStream - This is a stream of arithmetic, boolean, and stack operators and boolean constants. I end up enclosing it in the '{' and '}' braces for you, so don't do it yourself. This attribute is required. It's described on page 269 of the PDF 1.3 spec.

theFunctionType - The type of function which should be 4, as this is a Postscript calculator function

 public PDFFunction(int theFunctionType,
    List theDomain,
    List theRange,
    List theCZero,
    List theCOne,
    double theInterpolationExponentN) 
{
        super();
        this.functionType = 2;    // dang well better be 2;
        this.cZero = theCZero;
        this.cOne = theCOne;
        this.interpolationExponentN = theInterpolationExponentN;
        this.domain = theDomain;
        this.range = theRange;
}

create an complete Function object of Type 2, an Exponential Interpolation function. Use null for an optional object parameter if you choose not to use it. For optional int parameters, pass the default.

Parameters:

theDomain - List objects of Double objects. This is the domain of the function. See page 264 of the PDF 1.3 Spec.

theRange - List of Doubles that is the Range of the function. See page 264 of the PDF 1.3 Spec.

theCZero - This is a vector of Double objects which defines the function result when x=0. This attribute is optional. It's described on page 268 of the PDF 1.3 spec.

theCOne - This is a vector of Double objects which defines the function result when x=1. This attribute is optional. It's described on page 268 of the PDF 1.3 spec.

theInterpolationExponentN - This is the inerpolation exponent. This attribute is required. PDF Spec page 268

theFunctionType - The type of the function, which should be 2.

 public PDFFunction(int theFunctionType,
    List theDomain,
    List theRange,
    List theFunctions,
    List theBounds,
    List theEncode) 
{
        super();
        this.functionType = 3;    // dang well better be 3;
        this.functions = theFunctions;
        this.bounds = theBounds;
        this.encode = theEncode;
        this.domain = theDomain;
        this.range = theRange;
}

create an complete Function object of Type 3, a Stitching function. Use null for an optional object parameter if you choose not to use it. For optional int parameters, pass the default.

Parameters:

theDomain - List objects of Double objects. This is the domain of the function. See page 264 of the PDF 1.3 Spec.

theRange - List objects of Double objects. This is the Range of the function. See page 264 of the PDF 1.3 Spec.

theFunctions - A List of the PDFFunction objects that the stitching function stitches. This attributed is required. It is described on page 269 of the PDF spec.

theBounds - This is a vector of Doubles representing the numbers that, in conjunction with Domain define the intervals to which each function from the 'functions' object applies. It must be in order of increasing magnitude, and each must be within Domain. It basically sets how much of the gradient each function handles. This attributed is required. It's described on page 269 of the PDF 1.3 spec.

theEncode - List objects of Double objects. This is the linear mapping of input values intop the domain of the function's sample table. Default is hard to represent in ascii, but basically [0 (Size0 1) 0 (Size1 1)...]. This attribute is required. See page 270 in the PDF 1.3 spec.

theFunctionType - This is the function type. It should be 3, for a stitching function.

 public PDFFunction(int theFunctionType,
    List theDomain,
    List theRange,
    List theSize,
    int theBitsPerSample,
    int theOrder,
    List theEncode,
    List theDecode,
    StringBuffer theFunctionDataStream,
    List theFilter) 
{
    // See encode above, as it's also part of Type 3 Functions.
    /* *************************TYPE 4************************** */
    // See 'data' above.
        super();
        this.functionType = 0;      // dang well better be 0;
        this.size = theSize;
        this.bitsPerSample = theBitsPerSample;
        this.order = theOrder;      // int
        this.encode = theEncode;    // vector of int
        this.decode = theDecode;    // vector of int
        this.functionDataStream = theFunctionDataStream;
        this.filter = theFilter;    // vector of Strings
        // the domain and range are actually two dimensional arrays.
        // so if there's not an even number of items, bad stuff
        // happens.
        this.domain = theDomain;
        this.range = theRange;
}

create an complete Function object of Type 0, A Sampled function. Use null for an optional object parameter if you choose not to use it. For optional int parameters, pass the default.

Parameters:

theDomain - List objects of Double objects. This is the domain of the function. See page 264 of the PDF 1.3 Spec.

theRange - List objects of Double objects. This is the Range of the function. See page 264 of the PDF 1.3 Spec.

theSize - A List object of Integer objects. This is the number of samples in each input dimension. I can't imagine there being more or less than two input dimensions, so maybe this should be an array of length 2. See page 265 of the PDF 1.3 Spec.

theBitsPerSample - An int specifying the number of bits used to represent each sample value. Limited to 1,2,4,8,12,16,24 or 32. See page 265 of the 1.3 PDF Spec.

theOrder - The order of interpolation between samples. Default is 1 (one). Limited to 1 (one) or 3, which means linear or cubic-spline interpolation. This attribute is optional. See page 265 in the PDF 1.3 spec.

theEncode - List objects of Double objects. This is the linear mapping of input values intop the domain of the function's sample table. Default is hard to represent in ascii, but basically [0 (Size0 1) 0 (Size1 1)...]. This attribute is optional. See page 265 in the PDF 1.3 spec.

theDecode - List objects of Double objects. This is a linear mapping of sample values into the range. The default is just the range. This attribute is optional. Read about it on page 265 of the PDF 1.3 spec.

theFunctionDataStream - The sample values that specify the function are provided in a stream. This is optional, but is almost always used. Page 265 of the PDF 1.3 spec has more.

theFilter - This is a vector of String objects which are the various filters that have are to be applied to the stream to make sense of it. Order matters, so watch out. This is not documented in the Function section of the PDF 1.3 spec, it was deduced from samples that this is sometimes used, even if we may never use it in FOP. It is added for completeness sake.

theFunctionType - This is the type of function (0,2,3, or 4). It should be 0 as this is the constructor for sampled functions.

 public boolean equals(Object obj) 
{
        if (obj == null) {
            return false;
        }
        if (obj == this) {
            return true;
        }
        if (!(obj instanceof PDFFunction)) {
            return false;
        }
        PDFFunction func = (PDFFunction)obj;
        if (functionType != func.functionType) {
            return false;
        }
        if (bitsPerSample != func.bitsPerSample) {
            return false;
        }
        if (order != func.order) {
            return false;
        }
        if (interpolationExponentN != func.interpolationExponentN) {
            return false;
        }
        if (domain != null) {
            if (!domain.equals(func.domain)) {
                return false;
            }
        } else if (func.domain != null) {
            return false;
        }
        if (range != null) {
            if (!range.equals(func.range)) {
                return false;
            }
        } else if (func.range != null) {
            return false;
        }
        if (size != null) {
            if (!size.equals(func.size)) {
                return false;
            }
        } else if (func.size != null) {
            return false;
        }
        if (encode != null) {
            if (!encode.equals(func.encode)) {
                return false;
            }
        } else if (func.encode != null) {
            return false;
        }
        if (decode != null) {
            if (!decode.equals(func.decode)) {
                return false;
            }
        } else if (func.decode != null) {
            return false;
        }
        if (functionDataStream != null) {
            if (!functionDataStream.equals(func.functionDataStream)) {
                return false;
            }
        } else if (func.functionDataStream != null) {
            return false;
        }
        if (filter != null) {
            if (!filter.equals(func.filter)) {
                return false;
            }
        } else if (func.filter != null) {
            return false;
        }
        if (cZero != null) {
            if (!cZero.equals(func.cZero)) {
                return false;
            }
        } else if (func.cZero != null) {
            return false;
        }
        if (cOne != null) {
            if (!cOne.equals(func.cOne)) {
                return false;
            }
        } else if (func.cOne != null) {
            return false;
        }
        if (functions != null) {
            if (!functions.equals(func.functions)) {
                return false;
            }
        } else if (func.functions != null) {
            return false;
        }
        if (bounds != null) {
            if (!bounds.equals(func.bounds)) {
                return false;
            }
        } else if (func.bounds != null) {
            return false;
        }
        return true;
}

Check if this function is equal to another object. This is used to find if a particular function already exists in a document.

 public byte[] toPDF() 
{
        int vectorSize = 0;
        int numberOfFunctions = 0;
        int tempInt = 0;
        StringBuffer p = new StringBuffer(256);
        p.append(getObjectID()
                + "< <  \n/FunctionType " + this.functionType + " \n");
        // FunctionType 0
        if (this.functionType == 0) {
            if (this.domain != null) {
                // DOMAIN
                p.append("/Domain [ ");
                vectorSize = this.domain.size();
                for (tempInt = 0; tempInt <  vectorSize; tempInt++) {
                    p.append(PDFNumber.doubleOut((Double)this.domain.get(tempInt))
                             + " ");
                }
                p.append("] \n");
            } else {
                p.append("/Domain [ 0 1 ] \n");
            }
            // SIZE
            if (this.size != null) {
                p.append("/Size [ ");
                vectorSize = this.size.size();
                for (tempInt = 0; tempInt <  vectorSize; tempInt++) {
                    p.append(PDFNumber.doubleOut((Double)this.size.get(tempInt))
                             + " ");
                }
                p.append("] \n");
            }
            // ENCODE
            if (this.encode != null) {
                p.append("/Encode [ ");
                vectorSize = this.encode.size();
                for (tempInt = 0; tempInt <  vectorSize; tempInt++) {
                    p.append(PDFNumber.doubleOut((Double)this.encode.get(tempInt))
                             + " ");
                }
                p.append("] \n");
            } else {
                p.append("/Encode [ ");
                vectorSize = this.functions.size();
                for (tempInt = 0; tempInt <  vectorSize; tempInt++) {
                    p.append("0 1 ");
                }
                p.append("] \n");
            }
            // BITSPERSAMPLE
            p.append("/BitsPerSample " + this.bitsPerSample);
            // ORDER (optional)
            if (this.order == 1 || this.order == 3) {
                p.append(" \n/Order " + this.order + " \n");
            }
            // RANGE
            if (this.range != null) {
                p.append("/Range [ ");
                vectorSize = this.range.size();
                for (tempInt = 0; tempInt <  vectorSize; tempInt++) {
                    p.append(PDFNumber.doubleOut((Double)this.range.get(tempInt))
                             + " ");
                }
                p.append("] \n");
            }
            // DECODE
            if (this.decode != null) {
                p.append("/Decode [ ");
                vectorSize = this.decode.size();
                for (tempInt = 0; tempInt <  vectorSize; tempInt++) {
                    p.append(PDFNumber.doubleOut((Double)this.decode.get(tempInt))
                             + " ");
                }
                p.append("] \n");
            }
            // LENGTH
            if (this.functionDataStream != null) {
                p.append("/Length " + (this.functionDataStream.length() + 1)
                         + " \n");
            }
            // FILTER?
            if (this.filter != null) {           // if there's a filter
                vectorSize = this.filter.size();
                p.append("/Filter ");
                if (vectorSize == 1) {
                    p.append("/" + ((String)this.filter.get(0))
                             + " \n");
                } else {
                    p.append("[ ");
                    for (tempInt = 0; tempInt <  vectorSize; tempInt++) {
                        p.append("/" + ((String)this.filter.get(0))
                                 + " ");
                    }
                    p.append("] \n");
                }
            }
            p.append(" > > \n");
            // stream representing the function
            if (this.functionDataStream != null) {
                p.append("stream\n" + this.functionDataStream
                         + "\nendstream\n");
            }
            p.append("endobj\n");
            // end of if FunctionType 0
        } else if (this.functionType == 2) {
            // DOMAIN
            if (this.domain != null) {
                p.append("/Domain [ ");
                vectorSize = this.domain.size();
                for (tempInt = 0; tempInt <  vectorSize; tempInt++) {
                    p.append(PDFNumber.doubleOut((Double)this.domain.get(tempInt))
                             + " ");
                }
                p.append("] \n");
            } else {
                p.append("/Domain [ 0 1 ] \n");
            }
            // RANGE
            if (this.range != null) {
                p.append("/Range [ ");
                vectorSize = this.range.size();
                for (tempInt = 0; tempInt <  vectorSize; tempInt++) {
                    p.append(PDFNumber.doubleOut((Double)this.range.get(tempInt))
                             + " ");
                }
                p.append("] \n");
            }
            // FunctionType, C0, C1, N are required in PDF
            // C0
            if (this.cZero != null) {
                p.append("/C0 [ ");
                vectorSize = this.cZero.size();
                for (tempInt = 0; tempInt <  vectorSize; tempInt++) {
                    p.append(PDFNumber.doubleOut((Double)this.cZero.get(tempInt))
                             + " ");
                }
                p.append("] \n");
            }
            // C1
            if (this.cOne != null) {
                p.append("/C1 [ ");
                vectorSize = this.cOne.size();
                for (tempInt = 0; tempInt <  vectorSize; tempInt++) {
                    p.append(PDFNumber.doubleOut((Double)this.cOne.get(tempInt))
                             + " ");
                }
                p.append("] \n");
            }
            // N: The interpolation Exponent
            p.append("/N "
                     + PDFNumber.doubleOut(new Double(this.interpolationExponentN))
                     + " \n");
            p.append(" > > \nendobj\n");
        } else if (this.functionType
                   == 3) {                       // fix this up when my eyes uncross
            // DOMAIN
            if (this.domain != null) {
                p.append("/Domain [ ");
                vectorSize = this.domain.size();
                for (tempInt = 0; tempInt <  vectorSize; tempInt++) {
                    p.append(PDFNumber.doubleOut((Double)this.domain.get(tempInt))
                             + " ");
                }
                p.append("] \n");
            } else {
                p.append("/Domain [ 0 1 ] \n");
            }
            // RANGE
            if (this.range != null) {
                p.append("/Range [ ");
                vectorSize = this.range.size();
                for (tempInt = 0; tempInt <  vectorSize; tempInt++) {
                    p.append(PDFNumber.doubleOut((Double)this.range.get(tempInt))
                             + " ");
                }
                p.append("] \n");
            }
            // FUNCTIONS
            if (this.functions != null) {
                p.append("/Functions [ ");
                numberOfFunctions = this.functions.size();
                for (tempInt = 0; tempInt <  numberOfFunctions; tempInt++) {
                    p.append(((PDFFunction)this.functions.get(tempInt)).referencePDF()
                             + " ");
                }
                p.append("] \n");
            }
            // ENCODE
            if (this.encode != null) {
                p.append("/Encode [ ");
                vectorSize = this.encode.size();
                for (tempInt = 0; tempInt <  vectorSize; tempInt++) {
                    p.append(PDFNumber.doubleOut((Double)this.encode.get(tempInt))
                             + " ");
                }
                p.append("] \n");
            } else {
                p.append("/Encode [ ");
                vectorSize = this.functions.size();
                for (tempInt = 0; tempInt <  vectorSize; tempInt++) {
                    p.append("0 1 ");
                }
                p.append("] \n");
            }
            // BOUNDS, required, but can be empty
            p.append("/Bounds [ ");
            if (this.bounds != null) {
                vectorSize = this.bounds.size();
                for (tempInt = 0; tempInt <  vectorSize; tempInt++) {
                    p.append(PDFNumber.doubleOut((Double)this.bounds.get(tempInt))
                             + " ");
                }
            } else {
                if (this.functions != null) {
                    // if there are n functions,
                    // there must be n-1 bounds.
                    // so let each function handle an equal portion
                    // of the whole. e.g. if there are 4, then [ 0.25 0.25 0.25 ]
                    String functionsFraction = PDFNumber.doubleOut(new Double(1.0
                            / ((double)numberOfFunctions)));
                    for (tempInt = 0; tempInt + 1 <  numberOfFunctions;
                            tempInt++) {
                        p.append(functionsFraction + " ");
                    }
                    functionsFraction = null;    // clean reference.
                }
            }
            p.append("] \n");
            p.append(" > > \nendobj\n");
        } else if (this.functionType
                   == 4) {                       // fix this up when my eyes uncross
            // DOMAIN
            if (this.domain != null) {
                p.append("/Domain [ ");
                vectorSize = this.domain.size();
                for (tempInt = 0; tempInt <  vectorSize; tempInt++) {
                    p.append(PDFNumber.doubleOut((Double)this.domain.get(tempInt))
                             + " ");
                }
                p.append("] \n");
            } else {
                p.append("/Domain [ 0 1 ] \n");
            }
            // RANGE
            if (this.range != null) {
                p.append("/Range [ ");
                vectorSize = this.range.size();
                for (tempInt = 0; tempInt <  vectorSize; tempInt++) {
                    p.append(PDFNumber.doubleOut((Double)this.range.get(tempInt))
                             + " ");
                }
                p.append("] \n");
            }
            // LENGTH
            if (this.functionDataStream != null) {
                p.append("/Length " + (this.functionDataStream.length() + 1)
                         + " \n");
            }
            p.append(" > > \n");
            // stream representing the function
            if (this.functionDataStream != null) {
                p.append("stream\n{ " + this.functionDataStream
                         + " } \nendstream\n");
            }
            p.append("endobj\n");
        }
        return encode(p.toString());
}

represent as PDF. Whatever the FunctionType is, the correct representation spits out. The sets of required and optional attributes are different for each type, but if a required attribute's object was constructed as null, then no error is raised. Instead, the malformed PDF that was requested by the construction is dutifully output. This policy should be reviewed.