IMG_File.h

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/*
 * PROPRIETARY INFORMATION.  This software is proprietary to
 * Side Effects Software Inc., and is not to be reproduced,
 * transmitted, or disclosed in any way without written permission.
 *
 * NAME:        IMG_File.h ( IMG Library, C++)
 *
 * COMMENTS:
 *      Generic interface for loading and saving image files.
 */

#pragma once

#ifndef __IMG_File__
#define __IMG_File__

#include "IMG_API.h"
#include "IMG_Error.h"
#include "IMG_FileParms.h"
#include "IMG_FileTypes.h"
#include "IMG_Stat.h"
#include "IMG_Metadata.h"

#include <PXL/PXL_Forward.h>
#include <UT/UT_BitArray.h>
#include <UT/UT_Functor.h>
#include <UT/UT_Matrix4.h>
#include <UT/UT_NonCopyable.h>
#include <UT/UT_Rect.h>
#include <UT/UT_SharedPtr.h>
#include <UT/UT_UniquePtr.h>
#include <UT/UT_ValArray.h>
#include <SYS/SYS_Deprecated.h>
#include <SYS/SYS_Types.h>
#include <iosfwd>

class IMG_File;
class IMG_Metadata;
class IMG_Format;
class IMG_Plane;
class IMG_SaveRastersToFilesParms;
class PXL_DeepSampleList;
class PXL_Raster;
class FS_Reader;
class FS_Writer;
template <typename T> class UT_Array;
class UT_IStream;
class UT_Options;
class UT_String;
class UT_StringHolder;
class UT_StringRef;
class UT_WorkBuffer;

using IMG_FilePtr = UT_UniquePtr<IMG_File>;

typedef UT_Functor1<UT_IStream *,const UT_StringRef &> IMG_FileOpenHook;
typedef UT_Functor1<void, UT_IStream *> IMG_FileCloseHook;

/// @brief Generic interface for reading and writing image files.
/// This class handles the reading and writing of all image formats that Houdini
/// supports. Use the static open() or create() methods to get an IMG_File
/// instance to read to or write from. Deleting this instance will close the
/// file.
class IMG_API IMG_File
{
public:
    virtual ~IMG_File();
    UT_NON_COPYABLE(IMG_File)

    virtual int64 getMemoryUsage(bool inclusive) const;

    // The following methods are a public interface which is not dependent on
    // the format of the image.  Users of the library should use these methods
    // to do the loading and saving of the data.

    /// @brief Open an image file using a filename
    /// Open an image file for reading by specifying the filename and path of
    /// the file. An optional IMG_FileParms class may be passed to convert it
    /// into a specific image type (8bit, specific resolution, etc). An optional
    /// format may also be passed, which forces the library to assume the image
    /// file is of that particular format.
    /// This method returns a new IMG_File object which you read the image data 
    /// from, or NULL if an error occurred.
    static IMG_FilePtr  open(const char *filename,
                              const IMG_FileParms *options = nullptr,
                              const IMG_Format *fmt = nullptr);

    /// @brief Open an image file using a filename
    /// Open an image file for reading by specifying the filename and path of
    /// the file.  A list of formats is also given, allowing the caller
    /// customization of the types and order of formats.
    /// An optional IMG_FileParms class may be passed to convert it
    /// into a specific image type (8bit, specific resolution, etc).
    /// This method returns a new IMG_File object which you read the image data
    /// from, or NULL if an error occurred.
    static IMG_FilePtr  open(const char *filename,
                              const UT_Array<const IMG_Format*> &image_formats,
                              const IMG_FileParms *options = nullptr);

    /// @brief Open an image file from a stream
    /// Open an image file for reading given a stream. This is useful for 
    /// embedded images in a file. An optional IMG_FileParms class may be 
    /// passed to convert it into a specific image type (8bit, specific 
    /// resolution, etc). An optional format may also be passed, which forces
    /// the library to assume the image file is of that particular format.
    /// If 'steal_stream' is true, the image library assumes ownership of the
    /// stream and closes it when it's finished reading the file. If the stream
    /// is not seekable (cannot jump around in the file, such as with a pipe),
    /// set 'streamIsSeekable' to false.
    /// This method returns a new IMG_File object which you read the image data 
    /// from, or NULL if an error occurred.
    static IMG_FilePtr   open(UT_IStream &is,
                              const IMG_FileParms *options = nullptr,
                              const IMG_Format *fmt=nullptr,
                              int steal_stream = 0,
                              bool streamIsSeekable = true);

    /// @brief Create a new image file
    /// Create a new image file with the pathname 'filename' according to the
    /// parameters specified in 'stat'.  You can supply an optional 'options'
    /// class to translate the image before being written (scale, flip, etc). 
    /// You can also specify an optional 'format' parameter to force the file
    /// to be written as a specific image format (regardless of the extension
    /// found in 'filename'). 
    /// NULL may be returned if the file could not be created for any reason.
    static IMG_FilePtr   create(const char *filename,
                                const IMG_Stat &stat,
                                const IMG_FileParms *options = nullptr,
                                const IMG_Format *fmt = nullptr);

    
    /// @brief Write an image file to an existing stream
    /// Writes a new image file to the stream 'os' according to the
    /// parameters specified in 'stat'.  You can supply an optional 'options'
    /// class to translate the image before being written (scale, flip, etc). 
    /// You can also specify an optional 'format' parameter to force the file
    /// to be written as a specific image format (regardless of the extension
    /// found in 'filename').
    /// If 'steal_stream' is true, the image library assumes ownership of the
    /// stream and closes it when it's finished writing the file. If the stream
    /// is not seekable (cannot jump around in the file, such as with a pipe),
    /// set 'streamIsSeekable' to false.
    /// NULL may be returned if the file could not be created in the stream.
    static IMG_FilePtr   create(std::ostream &os,
                                const IMG_Stat &stat,
                                const IMG_FileParms *options = nullptr,
                                const IMG_Format *fmt = nullptr,
                                int steal_stream = 0,
                                bool streamIsSeekable = true);

    /// @{
    /// @brief Writes a PXL_Raster to an image file.
    /// Convenience method to write an image stored in a PXL_Raster to a disk 
    /// file.
    static bool         saveRasterAsFile(const char *filename,
                                const PXL_Raster *raster,
                                const IMG_SaveRastersToFilesParms &parms);
    static bool         saveRasterAsFile(const char *filename,
                                const PXL_Raster *raster,
                                const IMG_FileParms *fparms = nullptr,
                                const IMG_Format *format = nullptr);
    /// @}

    /// @brief Writes PXL_Raster's to image files.
    /// Convenience method to write images stored in PXL_Raster's to disk
    /// files.  The @c linear_planes parameter specifies a pattern of planes
    /// which should be written to in linear space.
    static bool         saveRastersAsFiles(const char *filename,
                                const IMG_SaveRastersToFilesParms &parms);

    /// @brief Copies an existing image file to another image file.
    /// Convenience method to copy an image file from one file to another.
    /// The image date may be altered if the formats of the two files are
    /// not the same (based on filename extension), or if an optional 'options'
    /// class is passed.
    static bool         copyToFile(const char *sourcename,
                                const char *destname,
                                const IMG_FileParms *options = nullptr);

    static bool         copyToFileFormat(const char *sourcename,
                                const char *formatname,
                                UT_String *destname = nullptr,
                                const IMG_FileParms *options = nullptr);

    /// @brief Copies an existing image file to a stream
    /// Convenience method to copy an image file to a stream. The image data
    /// may be altered if an optional 'options' class is passed, or if the 
    /// optional image 'format' parameter does not match the format of the 
    /// source image file.
    static bool         copyToStream(const char *sourcename,
                                     std::ostream &deststream,
                                     const IMG_FileParms *options = nullptr,
                                     const IMG_Format *format = nullptr);

    /// Check whether image integrity by reading all scanlines of image
    static bool checkIntegrity(const char *filename, UT_StringHolder &error);

    /// Check whether image integrity by reading all scanlines of image.
    /// @note You cannot have read from the IMG_File, nor will you be able to
    /// read from the IMG_File after calling this method.
    ///
    /// To work properly, there shoud be no filtering on the IMG_File, so it
    /// should be opened using: @code
    ///   IMG_FileParms  parms;
    ///   parms.readAsIs();
    ///   parms.orientImage(IMG_ORIENT_X_NONE, IMG_ORIENT_Y_NONE);
    ///   IMG_FilePtr    fp = IMG_File::open(filename, &parms);
    /// @endcode;
    static bool checkIntegrity(IMG_File *fp, UT_StringHolder &error);

    /// Returns the image file extension (including leading ".") that should
    /// be used when we are automatically saving COP generated texture maps
    /// to disk as part of a USD export operation.
    static const char *getAutoTextureSaveFileExtention();

    virtual const char  *className() const { return "IMG_File"; }
 
    /// Closes the file. Called by the destructor if needed , so 'delete file'
    /// will often take the place of this call. However, you won't receive any
    /// error information in that case, so you can call it directly.
    int                  close();

    /// Returns 1 if we are reading, 0 if writing.
    int                  getReadMode() const;

    /// @{
    /// Returns the image type of the format we just opened.
    IMG_ImageType        getImageType() const;
    /// @}

    /// @{
    /// Retrieve the file format description of the file. The format contains
    /// all information that is general to all files of this format type.
    const IMG_Format    *getFormat() const              { return myFormat; }
    void                 setFormat(const IMG_Format *f) { myFormat = f; }
    /// @}

    /// Get the image description of the current image file (resolution, data 
    /// format, etc). The returned class can be queried for all of the current
    ///  image file's statistics.
    /// @{
    const IMG_Stat      &getStat() const;
          IMG_Stat      &getStat();

    const IMG_Stat      &unfilteredStat() const
                            { return getUnfilteredFile()->myStat; }
    /// @}

    /// Get additional image information about the file that is specific
    /// to a particular format. Some formats do not have additional information.
    /// The information returned is human-readable in 'text'.
    virtual void         getAdditionalInfo(UT_String &text);

    /// Returns the option passed through IMG_FileParms.  This searches for
    /// format specific options (i.e. OpenEXR::compression).  It's possible to
    /// override the format name by passing the @c format_override argument.
    UT_StringHolder      getFileOption(const UT_StringRef &name) const;

    /// Access to the list of file options this file was saved with.
    /// @{
    int                  SYS_DEPRECATED(20.0) getNumOptions() const;
    UT_StringHolder      SYS_DEPRECATED(20.0) getOptionName(int i) const;
    UT_StringHolder      SYS_DEPRECATED(20.0) getOptionValue(int i) const;
    /// @}

    /// When reading or writing a file, the metadata will contain all the
    /// metadata options defined by the file (and values that the user has
    /// passed through the IMG_FileParms).
    ///
    /// When reading a file, the driver will also populate the metadata from
    /// any data stored in the file.
    const IMG_Metadata  &metadata() const { return unfilteredStat().metadata(); }

    /// @{
    /// Iterate over the file's metdata
    IMG_Metadata::const_iterator        beginMetadata() const
                                            { return metadata().begin(); }
    IMG_Metadata::const_iterator        endMetadata() const
                                            { return metadata().end(); }
    /// @}

    /// Search for specific metadata
    bool        findMetadata(const UT_StringRef &name,
                        IMG_MetadataItem &value) const
                {
                    return unfilteredStat().findMetadata(name, value);
                }

    /// @{
    /// Import metadata
    bool        importMetadata(const UT_StringRef &name, bool &value) const
                    { return unfilteredStat().importMetadata(name, value); }
    bool        importMetadata(const UT_StringRef &name, UT_StringHolder &value) const
                    { return unfilteredStat().importMetadata(name, value); }
    bool        importMetadata(const UT_StringRef &name, int32 &value) const
                    { return unfilteredStat().importMetadata(name, value); }
    bool        importMetadata(const UT_StringRef &name, int64 &value) const
                    { return unfilteredStat().importMetadata(name, value); }
    bool        importMetadata(const UT_StringRef &name, fpreal32 &value) const
                    { return unfilteredStat().importMetadata(name, value); }
    bool        importMetadata(const UT_StringRef &name, fpreal64 &value) const
                    { return unfilteredStat().importMetadata(name, value); }
    bool        importMetadata(const UT_StringRef &name, UT_Matrix4F &m) const
                    { return unfilteredStat().importMetadata(name, m); }
    bool        importMetadata(const UT_StringRef &name, UT_Matrix4D &m) const
                    { return unfilteredStat().importMetadata(name, m); }
    /// @}

    /// Convert metadata to a string value.  When @c pretty_print is @c true:
    /// - If there's a menu, the corresponding label will be returned
    /// - If there's type information, it will be used (i.e. printing a time or
    ///   memory)
    bool        metadataAsString(const UT_StringRef &name,
                        UT_StringHolder &value,
                        bool pretty_print = true) const
    {
        return unfilteredStat().metadataAsString(name, value, pretty_print);
    }

    /// @brief read a single scanline.
    /// read() returns a pointer to the scanline data
    /// in an internal buffer. Do not delete it.
    const void          *read(int scan, const IMG_Plane *from_plane = nullptr);

    /// @brief Reads the scanline into a buffer that you supply.
    /// The buffer passed must be big enough to fit the plane passed.
    /// getStat().bytesPerPlaneScan() will return the proper size.
    /// Returns 0 on failure.
    bool                 readIntoBuffer(int scan, void *buffer,
                                        const IMG_Plane *from_plane = nullptr);

    /// @brief Write a scanline to the file. 
    /// You don't need to write scanlines  in order, nor do you need to write 
    /// planes in order; the data may be cached however. Returns 0 if
    /// there was an error during the write. You should immediately stop
    /// writing if a failure occurred (many formats will behave unpredictably
    /// otherwise).
    bool                 write(int scan, const void *data,
                               const IMG_Plane *to_plane = nullptr);

    /// allocates a buffer large enough to hold the biggest plane's scanline
    /// in the file. Free this buffer with free(). (This will not hold all
    /// the planes' scanlines, only one at a time!)
    void *               allocScanlineBuffer() const;

    /// The size in bytes of the buffer allocated for a scanline.
    exint                getScanlineBufferSizeB() const;

    /// @deprecated
    /// The following methods read/write a whole raster.  Unless the scanline
    /// increment is passed in, the stat structure will be used to determine the
    /// scanline size.  Beware if you're using translators...
    /// Use readImages() and writeImages() instead.
    ///@{
    bool                 readImage(void *data, int flip=0, int scaninc=0);
    /// @deprecated
    bool                 writeImage(void *data, int flip=0, int scaninc=0);
    ///@}

    // Convenience method to write a single raster to a file.
    static bool writeImage(const UT_StringRef &filepath,
                           const PXL_Raster &image,
                           const IMG_FileParms *options = nullptr,
                           const IMG_Format *fmt = nullptr);

    /// @brief Reads all the image data into a list of PXL_Rasters.
    /// reads the image data into a a series of rasters. The array should be
    /// empty, as this method creates and fills the rasters for you.
    bool                 readImages(UT_Array<UT_UniquePtr<PXL_Raster>> &images,
                                    const char *scope = nullptr);

    /// @{
    /// @brief Writes all PXL_Rasters to the image format.
    /// This method takes a raster per IMG_Plane in the stat. The
    /// data format, color model and res of the raster must match the
    /// corresponding IMG_Plane. If the format is not a deep raster format,
    /// not all images may be written.
    /// if 'freerasters' is true, it will free the rasters for you.
    bool                 writeImages(const UT_Array<const PXL_Raster *> &imgs);
    bool                 writeImages(UT_Array<UT_UniquePtr<PXL_Raster>> &images,
                                    bool freerasters = false);
    /// @}

    /// @deprecated
    /// For image files that contain more than one image, such as a
    /// movie file, jump to a particular frame in the movie and reset 
    /// for reading the scanlines of the new frame
    virtual bool         jumpToFrame(int frame);

    /// When writing an image, call if interrupted or you encounter an
    /// non-image-file error and cannot complete the file write.
    virtual void         abortWrite();
    
    ///@{
    /// orientation of the current file or format. Some formats support multiple
    /// orientations specified in the image files themselves, others simply
    /// have a fixed orientation. Call these methods rather than querying the
    /// orientation from the format, in case the format supports multiple 
    /// orientations.
    virtual int          isTopFirst() const;
    /// If 0, scanlines are right-to-left. Default is 1 (left-to-right).
    virtual int          isLeftFirst() const;
    ///@}

    /// call this if you won't be reading the scanlines in order, or if
    /// you'll be reading all the scanlines for a single plane first.
    virtual void         randomReadAccessRequired();

    /// @{
    /// @private
    bool        randomReadsForced() const { return myForceRandomReads; }
    /// @}

    /// @{
    /// This is a tile interface for reading files. To use it, you must pass an
    /// IMG_FileParms object to open() with IMG_FileParms::useTileInterface()
    /// called. Otherwise, this will just return false. The x-y coords of the 
    ///tile is in pixels.
    virtual bool         readTile(const UT_InclusiveRect &tile, void *data,
                                  const IMG_Plane *plane=0);
    
    /// this is a tile interface for writing files. To use it, you must pass an
    /// IMG_FileParms object to open() with IMG_FileParms::useTileInterface()
    /// called. Otherwise, this will just return false. The x-y coords of the 
    ///tile is in pixels.
    virtual bool         writeTile(const UT_InclusiveRect &tile,
                                   const void *data,
                                   const IMG_Plane *plane=0);
    /// @}

    /// When writing an image, the checkpoint() method can be used to
    /// checkpoint data (see TIFFCheckpointDirectory() for an example).
    /// Generally, this writes the image data currently passed and this results
    /// in a usable, partially written file.
    /// By default, nothing is done.
    virtual void         checkpoint();

    /// This method converts the "standard" bit depth option to an IMG_DataType.
    /// This is used by the -b option in mantra as well as many other places.
    /// When dealing with floating point arguments, there's an optional flag to
    /// "denormalize" the floating point values when writing.  This basically
    /// removes tiny precision errors.  It's up to the user to deal with the
    /// denormalization.
    /// - char, byte, 8 = uint8
    /// - short, 16     = uint16
    /// - int           = uint32
    /// - FLOAT         = fpreal32 (denormalize=true)
    /// - HALF          = fpreal16 (denormalize=true)
    /// - float, 32     = fpreal32
    /// - half          = fpreal16
    static IMG_DataType         mapStorageOption(const char *option,
                                            bool *denormalize_flag = nullptr);

    /// Turns error reporting on or off. Returns the previous setting.
    /// Errors are reported to the error manager, which will either show up
    /// in the node information or the Houdini status bar (if not loaded within
    /// a node).
    ///
    static int           doErrors(int newDoErrors);
    static void          imgError(IMG_ErrorCodes code,
                                  const char *msg = nullptr);
    static void          imgWarning(IMG_ErrorCodes code,
                                    const char *msg = nullptr);

    bool                 hasError() const
                         { return getBaseFile() ? (getBaseFile()->hasError() ||
                                                   myErrorFlag) :myErrorFlag; }

    /// Returns information about the alpha channel if the IMG_FileParms passed
    /// to open() had detectAlphaDetails() specified. 
    virtual IMG_FileAlphaInfo getAlphaInfo(float &) const
                              { return IMG_ALPHA_VARYING; }
    
    /// returns the raw file at the top of the filter stack.
    IMG_File            *getUnfilteredFile();
    const IMG_File      *getUnfilteredFile() const;
    virtual IMG_File    *getBaseFile() const { return 0; }

    /// Copy the texture image options from another IMG_File
    bool                copyImageTextureOptions(const IMG_File &src,
                                bool clear_existing);

    /// Some image formats support "texture" options.  Formats which do not
    /// support options should return a NULL pointer.
    /// This method calls @c getImageTextureOptions() by default
    virtual UT_SharedPtr<UT_Options>    imageTextureOptions() const;

    /// This method is deprecated.  Please implement @c imageTextureOptions()
    SYS_DEPRECATED(12.0) virtual const UT_Options *getImageTextureOptions() const;

    /// For image formats which support texture options, this will clear out
    /// all texture options.
    virtual void        clearImageTextureOptions();

    /// For image formats which support texture options, merge the UT_Options
    /// into the current options.
    virtual bool        setImageTextureOptions(const UT_Options &options);

    /// When being created through a tile device (i.e. rendering, etc.), the
    /// writer may send additional information to the file writer after the
    /// image has been created.
    virtual void        setWriteTag(const char *tagname,
                                    int num_values,
                                    const char *const *values);

    /// Read the image options (@see getOption()) to extract the world to
    /// camera transform.  If the data isn't available, this method returns
    /// false.  This will likely only work when the image is being created from
    /// mantra.
    bool        getWorldToCamera(UT_Matrix4D &xform) const;

    /// Read the image options (@see getOption()) to extract the camera to NDC
    /// transform.  If the data isn't available in the options, this method
    /// returns false.  This will likely only work when the image is being
    /// created from mantra.
    /// If the @c fit_z option is true, the near/far range will be set to
    /// (0,1).  This will not be possible if the "camera:clip" setting wasn't
    /// passed in the options.
    bool        getCameraToNDC(UT_Matrix4D &xform, int xres, int yres, bool
                    fit_z = true) const;
    /// Read the image options (@see getOption()) to extract the world to NDC
    /// transform.  If the data isn't available in the options, this method
    /// returns false.  This will likely only work when the image is being
    /// created from mantra.
    /// If the @c fit_z option is true, the near/far range will be set to
    /// (0,1).  This will not be possible if the "camera:clip" setting wasn't
    /// passed in the options.
    bool        getWorldToNDC(UT_Matrix4D &xform, int xres, int yres, bool
                    fit_z = true) const;


    // API for raw deep pixel access.  Methods will fail if the image is not
    // a deep pixel image. The deep pixel functions can be accessed from
    // multiple threads simultaneously.

    // Returns the number of deep pixel samples for the given pixel location.
    // Returns -1 if the sample count cannot be read, or if the image is not
    // a deep pixel image.
    virtual int          getDeepPixelSamples(int x, int y);

    // Read the deep pixel samples for the given plane. The size of the data
    // array should be at least the same size as the number of samples returned
    // by getDeepPixelSamples multiplied by the component count of the plane
    // given by IMG_Plane::getComponentCount.
    // Returns false if the data cannot be read, or if the image is not a deep
    // pixel image.
    virtual bool         getDeepPixelPlaneData(int x, int y,
                                               const IMG_Plane &plane,
                                               float *data);

    // Read the deep pixel samples for all components at a given pixel location.
    // The length of the pointer array should at least be the same as the
    // number of samples returned from getDeepPixelSamples(). The size of
    // each array pointed to should be at least the same size as the number
    // of components returned from getDeepPixelComponentCount().
    // Returns false if the data cannot be read, of if the image is not a deep
    // pixel image.
    virtual bool         getDeepPixelData(int x, int y, float * const *data);

    /// Read a deep pixel
    virtual bool         readDeepPixelData(int x, int y,
                                        PXL_DeepSampleList &pixel);

    /// @{
    /// A method to write deep pixel data for all channels, at a given pixel
    /// location. The function should be given an array of pointers to float
    /// arrays, where each float array contains the value of all image
    /// components for a given sample level.
    ///
    /// Returns false if the data cannot be written, or if the image is not
    /// a deep pixel image.
    virtual bool         writeDeepPixelData(int x, int y,
                                            const PXL_DeepSampleListPtr &pixel);
    /// @}


    /// users of IMG_File can select only certain planes to read using
    /// IMG_FileParms::selectPlane..(). Call selectPlanesToRead() first,
    /// usually at the end of open(), and then call isPlaneSelected() to
    /// determine if the plane was selected for read.
    /// @{
    void                 selectPlanesToRead();
    bool                 isPlaneSelected(const IMG_Plane &plane) const;
    /// @}

    static void          setFileCreateCB(
                                UT_Functor1<int, const UT_StringRef &> cb);
    static void          setFileHooks(IMG_FileOpenHook openhook,
                                IMG_FileCloseHook closehook);
    static IMG_FileOpenHook     &getOpenHook();
    static IMG_FileCloseHook    &getCloseHook();

protected:
    IMG_File();         /// Only called by format class

    // If the check_magic flag is 0, then the first 4 bytes of the file have
    // alread.  They are passed in as the magic number for verification.
    virtual int          open();
    virtual int          openPostMagic();
    virtual int          openFile(const char *filename);

    virtual int          readScanline(int scanline, void *data) = 0;
    virtual const void  *readPlaneScanline(int y, const IMG_Plane &pi);

    // Create an image
    virtual int          createFile(const char *filename,const IMG_Stat &stat);
    virtual int          create(const IMG_Stat &stat);

    virtual int          writeScanline(int scanline, const void *data) = 0;
    virtual int          writePlaneScanline(const void *data, int y,
                                            const IMG_Plane &pi);

    virtual int          closeFile() = 0;

    /// Run after the output stream has been closed.
    /// Be careful, since some things have been destructed.
    virtual void         postCloseAction();

    // add any image flips, scales, data translations, etc. Returns the
    // end of the filter chain.
    //
    virtual bool         isPassThrough() const { return false; }

    // if you override this, you must call this class's version.
    virtual void         computeCommonData();

    void                *getScanlineBuffer(int y);
    void                *getPlaneBuffer(int y, const IMG_Plane &pi);

    virtual void         finishedScanline(int scan);

    static void          setOptions(const IMG_FileParms *options,
                                    IMG_File *file);

    /// @{
    /// Set option to control behaviour of the file.  For example, the
    /// compression level when creating the image.
    bool        setOption(const UT_StringHolder &token, const char *value);
    bool        setOption(const UT_StringHolder &token, fpreal64 val);
    bool        setOption(const UT_StringHolder &token, int64 val);
    bool        setOption(const UT_StringHolder &option, int value)
                        { return setOption(option, (int64)value); }

    bool        addMetadata(const UT_StringHolder &key,
                            const IMG_MetadataItem &item);
    bool        addMetadata(const UT_StringHolder &key,
                            const UT_JSONValue &value,
                            IMG_Metadata::Storage store =
                                    IMG_Metadata::Storage::MD_Unknown,
                            IMG_Metadata::TypeInfo type_info =
                                    IMG_Metadata::TypeInfo::MD_None);
    /// @}

    bool                 canWriteStatWithoutConversion() const;

    // Access to input and output streams
    //  peekByte() will peek at the next input byte.  -1 returned on EOF
    //  readSomeBytes() will read data into the buffer specified.  The number
    //          of bytes actually read is returned.
    //  writeSomeBytes() will write data from the buffer.  The number
    //          of bytes actually written is returned.
    //  flushBytes() will flush the output stream
    //  readBytes() is a convenience method when all data needs to be read
    //  writeBytes() is a convenience method when all data needs to be written
    // 
    int                  peekByte();
    int                  readSomeBytes(void *buffer, int size);
    int                  writeSomeBytes(const void *buffer, int size);
    bool                 flushBytes();

    bool                 readBytes(void *buffer, int size)
                         { return readSomeBytes(buffer, size) == size; }
    bool                 writeBytes(const void *buffer, int size)
                         { return writeSomeBytes(buffer, size) == size; }


    // For the odd format which requires data to be read as ASCII lines, this
    // method exists.
    bool                 readAsciiLine(UT_WorkBuffer &wbuf);

    // Seeks the stream to the start + offset.  Returns true if successful
    // and false otherwise.
    bool                 seekFromBeginning(int64 offset);
    bool                 seekFromCurrent(int64 offset);
    bool                 seekFromEnd(int64 offset);
    int64                tellCurrentPosition();

    // Copies our input stream to the given stream.
    void                 copyInputToStream(std::ostream &os);

    // Deletes our input stream.
    void                 deleteStream();

    /////////////////////////////////////////////////////////////////////////
    // Do not use these methods.  They are for special cases only.
    UT_IStream          *getUTIStream() { return myIStream; }
    void                 setIStream(UT_IStream *is)     { myIStream = is; }
    /////////////////////////////////////////////////////////////////////////

    // Image description.
    IMG_Stat             myStat;
    bool                 myReadMode;
    std::ostream        *myOS;
    int64                myStreamStartPos;
    int64                myStreamLength;
    unsigned             myCreateIStream:1,
                         myCreateOStream:1,
                         myForceRandomReads:1,
                         myHasRandomReads:1,
                         myFileOpen:1,
                         myErrorFlag:1,
                         myContinueOnErrorFlag:1,
                         myIStreamFromHook:1,
                         myExplicitFormat:1;

private:
    class img_ScanProgress
    {
    public:
                         img_ScanProgress()
                             : myNumPlanes(0)
                         {
                         }
        void             init(const IMG_Stat &stat);
        int64            getMemoryUsage(bool inclusive) const;
        void             processed(int scan, const IMG_Plane *plane);
        void             processAll(int scan);
        bool             isComplete(int scan, const IMG_Plane *plane) const;
        bool             isComplete(int scan) const;
        int              remaining(int scan) const;
        int              numScans() const { return myCounts.entries(); }
    private:
        int              bitIndex(int scan, int plane) const;
    private:
        int              myNumPlanes;
        UT_BitArray      myProcessed;
        UT_ValArray<int> myCounts;
    };

    // Initialize tags to default values
    void                 initializeTags();
    void                 makeScanlineBuffers();
    void                 deallocScanlineBuffer(int scan);
    const void          *returnErrorScan(int scan, const IMG_Plane &pi);
    const char          *metadataKey() const;

    static IMG_FilePtr  makeReadFilters(IMG_FilePtr src, const IMG_FileParms &parms);
    static IMG_FilePtr  makeWriteFilters(IMG_FilePtr src, const IMG_FileParms &parms);
    IMG_File    *makeDataConversion(const IMG_FileParms &parms,
                                IMG_File *file);
    IMG_File    *makeFlip(const IMG_FileParms &parms,
                                IMG_File *file);

    static IMG_FilePtr   open(const char *filename,
                            const IMG_FileParms *options,
                            const IMG_Format *fmt,
                            const UT_Array<const IMG_Format*> *image_formats);

    const IMG_Format            *myFormat;
    void                        *myScanlineBuffer;
    int                          myCurrentImageScanline;

    img_ScanProgress             myScanProgress;
    UT_ValArray<void *>          myImageScanline;
    UT_BitArray                  mySelectPlane;

    UT_UniquePtr<FS_Reader>      myReader;
    UT_UniquePtr<FS_Writer>      myWriter;
    UT_IStream                  *myIStream;

    // only IMG_Format can call initializeTags().
    friend class IMG_Format;
    friend class IMG_FileFilter;
    friend class IMG_GZip;
    friend class IMG_FileBuffer;
    friend class IMG_MemoryFileBuffer;
    friend class MV_ReadPRISMS;
};

/// Auto-scope class mainly to disable file errors temporarily
class IMG_API IMG_AutoFileError
{
public:
    IMG_AutoFileError(bool report_errors = false)
    {  myReport = IMG_File::doErrors(report_errors?1:0); }
    ~IMG_AutoFileError()
    { IMG_File::doErrors(myReport); }
    UT_NON_COPYABLE(IMG_AutoFileError);
private:
    int myReport = 1;
};

#endif