TIFFRGBAImage - read and decode an image into a raster

       To use the core support for reading and processing  TIFF images, but write the resulting raster data in a
       different format one need only override the "put methods" used to store raster data.  These  methods  are
       are  defined  in  the  TIFFRGBAImage  structure  and  initially setup by TIFFRGBAImageBegin() to point to
       routines that pack raster data in the default  ABGR  pixel  format.   Two  different  routines  are  used
       according  to  the  physical  organization of the image data in the file: PlanarConfiguration = 1 (packed
       samples), and PlanarConfiguration = 2 (separated samples).  Note that  this  mechanism  can  be  used  to
       transform the data before storing it in the raster.  For example one can convert data to colormap indices
       for display on a colormap display.

       LibTIFF contributors

       1988-2022, LibTIFF contributors

4.7                                               Apr 30, 2025                              TIFFRGBAIMAGE(3tiff)

       The  routines  described  here  provide a high-level interface through which TIFF images may be read into
       memory.  Images may be strip- or tile-based and have a variety of different characteristics: bits/sample,
       samples/pixel, photometric, etc.  Decoding state is encapsulated in a TIFFRGBAImage structure  making  it
       possible  to capture state for multiple images and quickly switch between them.  The target raster format
       can be customized to a particular application's needs by installing custom routines that manipulate image
       data according to application requirements.

       The default usage for these routines is:

       • check if an image can be processed using TIFFRGBAImageOK()

       • construct a decoder state block using TIFFRGBAImageBegin()

       • read and decode an image into a target raster using TIFFRGBAImageGet(), and then

       • release resources using TIFFRGBAImageEnd()TIFFRGBAImageGet() can be called multiple times to decode an image using different state parameters.   If
       multiple  images  are  to  be  displayed  and  there is not enough space for each of the decoded rasters,
       multiple state blocks can be managed and then calls can  be  made  to  TIFFRGBAImageGet()  as  needed  to
       display an image.

       The generated raster is assumed to be an array of width × height 32-bit entries, where width must be less
       than  or equal to the width of the image (height may be any non-zero size).  If the raster dimensions are
       smaller than the image, the image data is cropped to the raster bounds.  If the raster height is  greater
       than  that  of the image, then the image data are placed in the lower part of the raster.  (Note that the
       raster is assume to be organized such that the pixel at location (x, y) is raster [ y × width + x ]; with
       the raster origin in the lower-lefthandcorner.)

       Raster pixels are 8-bit packed red, green, blue, alpha samples.  The macros TIFFGetR, TIFFGetG, TIFFGetB,
       and TIFFGetA should be used to access  individual  samples.   Images  without  Associated  Alpha  matting
       information have a constant Alpha of 1.0 (255).

       TIFFRGBAImageGet()  converts  non-8-bit  images  by  scaling sample values.  Palette, grayscale, bilevel,
       CMYK, and YCbCr images are converted to RGB transparently.  Raster pixels are returned uncorrected by any
       colorimetry information present in the directory.

       The parameter stopOnError specifies how to act if an error is encountered while reading  the  image.   If
       stopOnError  is  non-zero,  then an error will terminate the operation; otherwise TIFFRGBAImageGet() will
       continue processing data until all the possible data in the image have been requested.

       All error messages are directed to the TIFFErrorExtR() routine.

       "Sorry,cannothandle%d-bitpictures":
          The image had BitsPerSample other than 1, 2, 4, 8, or 16.

       "Sorry,cannothandle%d-channelimages":
          The image had SamplesPerPixel other than 1, 3, or 4.

       Missingneeded"PhotometricInterpretation"tag:
          The image did not have a tag that describes how to display the data.

       No"PhotometricInterpretation"tag,assumingRGB:
          The image was missing a tag that describes how to display it, but because it has 3 or 4 samples/pixel,
          it is assumed to be RGB.

       No"PhotometricInterpretation"tag,assumingmin-is-black:
          The image was missing a tag that describes how to display it, but because it has 1 sample/pixel, it is
          assumed to be a grayscale or bilevel image.

       "Nospaceforphotometricconversiontable":
          There was insufficient memory for a table used to convert image samples to 8-bit RGB.

       Missingrequired"Colormap"tag:
          A Palette image did not have a required Colormap tag.

       "Nospacefortilebuffer":
          There was insufficient memory to allocate an i/o buffer.

       "Nospaceforstripbuffer":
          There was insufficient memory to allocate an i/o buffer.

       "Cannothandleformat":
          The  image  has a format (combination of BitsPerSample, SamplesPerPixel and PhotometricInterpretation)
          that can not be handled.

       "NospaceforB&Wmappingtable":
          There was insufficient memory to allocate a table used to map grayscale data to RGB.

       "NospaceforPalettemappingtable":
          There was insufficient memory to allocate a table used to map data to 8-bit RGB.

       TIFFRGBAImage - read and decode an image into a raster

       Samples  must  be  either  1,  2, 4, 8, or 16 bits.  Colorimetric samples/pixel must be either 1, 3, or 4
       (i.e.  SamplesPerPixel -ExtraSamples).

       Palette image colormaps that appear to be incorrectly written as 8-bit values are automatically scaled to
       16-bits.

       All routines return 1 if the operation was  successful.   Otherwise,  0  is  returned  if  an  error  was
       encountered and stopOnError is zero.

TIFFOpen (3tiff), TIFFReadRGBAImage (3tiff), TIFFReadRGBAStrip (3tiff), TIFFReadRGBATile (3tiff), libtiff
       (3tiff)

       It  is  simple  to  display  an  image  as  it is being read into memory by overriding the put methods as
       described above for supporting alternate raster formats.  Simply keep a  reference  to  the  default  put
       methods  setup  by  TIFFRGBAImageBegin() and then invoke them before or after each display operation. For
       example, the tiffgt utility uses the following put method to update the display as the  raster  is  being
       filled:

          static void
          putContigAndDraw(TIFFRGBAImage* img, uint32_t* raster,
              uint32_t x, uint32_t y, uint32_t w, uint32_t h,
              int32_t fromskew, int32_t toskew,
              unsigned char* cp)
          {
              (*putContig)(img, raster, x, y, w, h, fromskew, toskew, cp);
              if (x+w == width) {
                  w = width;
                  if (img->orientation == ORIENTATION_TOPLEFT)
                      lrectwrite(0, y-(h-1), w-1, y, raster-x-(h-1)*w);
                  else
                      lrectwrite(0, y, w-1, y+h-1, raster);
              }
          }

       (the original routine provided by the library is saved in the variable putContig.)

       The  TIFFRGBAImage()  routines  support the most commonly encountered flavors of TIFF.  It is possible to
       extend this support by overriding the "get method" invoked by TIFFRGBAImageGet() to read TIFF image data.
       Details of doing this are a bit involved, it is best to make a copy of an existing get method and  modify
       it to suit the needs of an application.

          #include <tiffio.h>

       typedefunsignedcharTIFFRGBValuetypedefstruct_TIFFRGBAImageTIFFRGBAImageintTIFFRGBAImageOK(TIFF*tif,charemsg[1024])intTIFFRGBAImageBegin(TIFFRGBAImage*img,TIFF*tif,intstopOnError,charemsg[1024])intTIFFRGBAImageGet(TIFFRGBAImage*img,uint32_t*raster,uint32_twidth,uint32_theight)voidTIFFRGBAImageEnd(TIFFRGBAImage*img)