QPDFStreamFilter.hh
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// Copyright (c) 2005-2020 Jay Berkenbilt
//
// This file is part of qpdf.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// Versions of qpdf prior to version 7 were released under the terms
// of version 2.0 of the Artistic License. At your option, you may
// continue to consider qpdf to be licensed under those terms. Please
// see the manual for additional information.
#ifndef QPDFSTREAMFILTER_HH
#define QPDFSTREAMFILTER_HH
#include <qpdf/DLL.h>
#include <qpdf/QPDFObjectHandle.hh>
#include <qpdf/Pipeline.hh>
class QPDF_DLL_CLASS QPDFStreamFilter
{
public:
QPDF_DLL
QPDFStreamFilter() = default;
QPDF_DLL
virtual ~QPDFStreamFilter() = default;
// A QPDFStreamFilter class must implement, at a minimum,
// setDecodeParms() and getDecodePipeline(). QPDF will always call
// setDecodeParms() before calling getDecodePipeline(). It is
// expected that you will store any needed information from
// decode_parms (or the decode_parms object iself) in your
// instance so that it can be used to construct the decode
// pipeline.
// Return a boolean indicating whether your filter can proceed
// with the given /DecodeParms. The default implementation accepts
// a null object and rejects everything else.
QPDF_DLL
virtual bool setDecodeParms(QPDFObjectHandle decode_parms);
// Return a pipeline that will decode data encoded with your
// filter. Your implementation must ensure that the pipeline is
// deleted when the instance of your class is destroyed.
QPDF_DLL
virtual Pipeline* getDecodePipeline(Pipeline* next) = 0;
// If your filter implements "specialized" compression or lossy
// compression, override one or both of these methods. The default
// implementations return false. See comments in QPDFWriter for
// details. QPDF defines specialized compression as non-lossy
// compression not intended for general-purpose data. qpdf, by
// default, doesn't mess with streams that are compressed with
// specialized compression, the idea being that the decision to
// use that compression scheme would fall outside of what
// QPDFWriter would know anything about, so any attempt to decode
// and re-encode would probably be undesirable.
QPDF_DLL
virtual bool isSpecializedCompression();
QPDF_DLL
virtual bool isLossyCompression();
private:
QPDFStreamFilter(QPDFStreamFilter const&) = delete;
QPDFStreamFilter& operator=(QPDFStreamFilter const&) = delete;
};
#endif // QPDFSTREAMFILTER_HH