mirror of https://github.com/qpdf/qpdf.git
69 lines
2.9 KiB
C++
69 lines
2.9 KiB
C++
// Copyright (c) 2005-2024 Jay Berkenbilt
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//
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// This file is part of qpdf.
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
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// in compliance with the License. You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software distributed under the License
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// is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
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// or implied. See the License for the specific language governing permissions and limitations under
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// the License.
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//
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// Versions of qpdf prior to version 7 were released under the terms of version 2.0 of the Artistic
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// License. At your option, you may continue to consider qpdf to be licensed under those terms.
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// Please see the manual for additional information.
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#ifndef QPDFSTREAMFILTER_HH
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#define QPDFSTREAMFILTER_HH
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#include <qpdf/DLL.h>
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#include <qpdf/Pipeline.hh>
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#include <qpdf/QPDFObjectHandle.hh>
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class QPDF_DLL_CLASS QPDFStreamFilter
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{
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public:
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QPDF_DLL
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QPDFStreamFilter() = default;
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QPDF_DLL
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virtual ~QPDFStreamFilter() = default;
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// A QPDFStreamFilter class must implement, at a minimum, setDecodeParms() and
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// getDecodePipeline(). QPDF will always call setDecodeParms() before calling
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// getDecodePipeline(). It is expected that you will store any needed information from
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// decode_parms (or the decode_parms object itself) in your instance so that it can be used to
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// construct the decode pipeline.
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// Return a boolean indicating whether your filter can proceed with the given /DecodeParms. The
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// default implementation accepts a null object and rejects everything else.
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QPDF_DLL
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virtual bool setDecodeParms(QPDFObjectHandle decode_parms);
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// Return a pipeline that will decode data encoded with your filter. Your implementation must
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// ensure that the pipeline is deleted when the instance of your class is destroyed.
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QPDF_DLL
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virtual Pipeline* getDecodePipeline(Pipeline* next) = 0;
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// If your filter implements "specialized" compression or lossy compression, override one or
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// both of these methods. The default implementations return false. See comments in QPDFWriter
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// for details. QPDF defines specialized compression as non-lossy compression not intended for
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// general-purpose data. qpdf, by default, doesn't mess with streams that are compressed with
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// specialized compression, the idea being that the decision to use that compression scheme
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// would fall outside of what QPDFWriter would know anything about, so any attempt to decode and
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// re-encode would probably be undesirable.
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QPDF_DLL
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virtual bool isSpecializedCompression();
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QPDF_DLL
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virtual bool isLossyCompression();
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private:
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QPDFStreamFilter(QPDFStreamFilter const&) = delete;
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QPDFStreamFilter& operator=(QPDFStreamFilter const&) = delete;
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};
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#endif // QPDFSTREAMFILTER_HH
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