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/*******************************************************************************
* gif.cpp
*
* This module contains the code to read the GIF file format.
*
* NOTE: Portions of this module were written by Steve Bennett and are used
* here with his permission.
*
* ---------------------------------------------------------------------------
* Persistence of Vision Ray Tracer ('POV-Ray') version 3.7.
* Copyright 1991-2013 Persistence of Vision Raytracer Pty. Ltd.
*
* POV-Ray is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* POV-Ray is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*********************************************************************************/
/*
* The following routines were borrowed freely from FRACTINT, and represent
* a generalized GIF file decoder.
*
* Swiped and converted to entirely "C" coded routines by AAC for the most
* in future portability!
*/
#include <vector>
// configbase.h must always be the first POV file included within base *.cpp files
#include "base/configbase.h"
#include "base/image/image.h"
#include "base/image/gif.h"
#include <boost/thread.hpp>
// this must be the last file included
#include "base/povdebug.h"
namespace pov_base
{
namespace Gif
{
// TODO: make sure we don't leak an image object if we throw an exception.
Image *Read (IStream *file, const Image::ReadOptions& options, bool IsPOTFile)
{
int data ;
int width;
int height;
Image *image = NULL;
unsigned char buffer[256];
vector<Image::RGBAMapEntry> colormap ;
int alphaIdx = -1; // assume no transparency color
// GIF files used to have no clearly defined gamma by default, but a W3C recommendation exists for them to use sRGB.
// Anyway, use whatever the user has chosen as default.
GammaCurvePtr gamma;
if (options.gammacorrect)
{
if (options.defaultGamma)
gamma = TranscodingGammaCurve::Get(options.workingGamma, options.defaultGamma);
else
gamma = TranscodingGammaCurve::Get(options.workingGamma, SRGBGammaCurve::Get());
}
int status = 0;
/* Get the screen description. */
if (!file->read (buffer, 13))
throw POV_EXCEPTION(kFileDataErr, "Cannot read GIF file header");
/* Use updated GIF specs. */
if (memcmp (buffer, "GIF", 3) != 0)
throw POV_EXCEPTION(kFileDataErr, "File is not in GIF format");
if (buffer[3] != '8' || (buffer[4] != '7' && buffer[4] != '9') || buffer[5] < 'A' || buffer[5] > 'z')
throw POV_EXCEPTION(kFileDataErr, "Unsupported GIF version");
int planes = ((unsigned) buffer [10] & 0x0F) + 1;
int colourmap_size = (1 << planes);
/* Color map (better be!) */
if ((buffer[10] & 0x80) == 0)
throw POV_EXCEPTION(kFileDataErr, "Error in GIF color map");
for (int i = 0; i < colourmap_size ; i++)
{
Image::RGBAMapEntry entry;
if (!file->read (buffer, 3))
throw POV_EXCEPTION(kFileDataErr, "Cannot read GIF colormap");
entry.red = IntDecode(gamma, buffer[0], 255);
entry.green = IntDecode(gamma, buffer[1], 255);
entry.blue = IntDecode(gamma, buffer[2], 255);
entry.alpha = 1.0f;
colormap.push_back(entry);
}
/* Now read one or more GIF objects. */
bool finished = false;
while (!finished)
{
switch (file->Read_Byte())
{
case EOF:
throw POV_EXCEPTION(kFileDataErr, "Unexpected EOF reading GIF file");
finished = true;
break ;
case ';': /* End of the GIF dataset. */
finished = true;
status = 0;
break;
case '!': /* GIF Extension Block. */
/* Read (and check) the ID. */
if (file->Read_Byte() == 0xF9)
{
if ((data = file->Read_Byte()) > 0)
{
if (!file->read (buffer, data))
throw POV_EXCEPTION(kFileDataErr, "Unexpected EOF reading GIF file");
// check transparency flag, and set transparency color index if appropriate
if (data >= 3 && buffer[0] & 0x01)
{
int alphaIdx = buffer[3];
if (alphaIdx < colourmap_size)
colormap[alphaIdx].alpha = 0.0f;
}
}
else
break;
}
while ((data = file->Read_Byte()) > 0)
if (!file->read (buffer, data))
throw POV_EXCEPTION(kFileDataErr, "Unexpected EOF reading GIF file");
break;
case ',': /* Start of image object. Get description. */
for (int i = 0; i < 9; i++)
{
if ((data = file->Read_Byte()) == EOF)
throw POV_EXCEPTION(kFileDataErr, "Unexpected EOF reading GIF file");
buffer[i] = (unsigned char) data;
}
/* Check "interlaced" bit. */
if ((buffer[9] & 0x40) != 0)
throw POV_EXCEPTION(kFileDataErr, "Interlacing in GIF image unsupported");
width = (int) buffer[4] | ((int) buffer[5] << 8);
height = (int) buffer[6] | ((int) buffer[7] << 8);
image = Image::Create (width, height, Image::Colour_Map, colormap) ;
// [CLi] GIF only uses full opacity or full transparency, so premultiplied vs. non-premultiplied alpha is not an issue
/* Get bytes */
Decode (file, image);
finished = true;
break;
default:
status = -1;
finished = true;
break;
}
}
if (!image)
throw POV_EXCEPTION(kFileDataErr, "Cannot find GIF image data block");
if (IsPOTFile == false)
return (image);
// POT files are GIF files where the right half of the image contains
// a second byte for each pixel on the left, thus allowing 16-bit
// indexes. In this case the palette data is ignored and we convert
// the image into a 16-bit grayscale version.
if ((width & 0x01) != 0)
throw POV_EXCEPTION(kFileDataErr, "Invalid width for POT file");
int newWidth = width / 2 ;
Image *newImage = Image::Create (newWidth, height, Image::Gray_Int16) ;
for (int y = 0 ; y < height ; y++)
for (int x = 0 ; x < newWidth ; x++)
newImage->SetGrayValue (x, y, (unsigned int) image->GetIndexedValue (x, y) << 8 | image->GetIndexedValue (x + newWidth, y)) ;
// NB: POT files don't use alpha, so premultiplied vs. non-premultiplied is not an issue
// NB: No gamma adjustment happening here!
delete image ;
return (newImage) ;
}
} // end of namespace Gif
}
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