Jpeg Namespace Reference

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Detailed Description

A wrapper around the libjpeg provinding higher level C++ functions

Functions
bool	CompressToBuffer (unsigned char *srcBuffer, int width, int height, int bpp, unsigned char *dstBuffer, int &len, int quality=75)
	Compresses an image buffer to a JPEG image in memory.
TL_DLL bool	CompressToFile (unsigned char *buffer, int width, int height, int bpp, const std::string &fileName, int quality=75)
	Compresses an image buffer to a JPEG image file.
bool	CompressToFile (unsigned char *buffer, int width, int height, int bpp, const string &fileName, int quality=75)
bool	DecompressBuffer (unsigned char *srcBuffer, int size, unsigned char *dstBuffer, int &width, int &height, int &bpp)
	Decompresses a JPEG image buffer to a buffer in memory.
TL_DLL bool	DecompressFile (const std::string &fileName, unsigned char *dstBuffer, int &width, int &height, int &nChannels)
	Reads and decompresses a JPEG image file to a buffer in memory.
bool	DecompressFile (const string &fileName, unsigned char *dstBuffer, int &width, int &height, int &nChannels)
TL_DLL bool	ReadFileParams (const std::string &fileName, int &width, int &height, int &nChannels)
	Reads the main informations about a JPEG image file.
bool	ReadFileParams (const string &fileName, int &width, int &height, int &nChannels)

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Function Documentation

TL_DLL bool Jpeg::CompressToBuffer	(	unsigned char *	srcBuffer,
		int	width,
		int	height,
		int	bpp,
		unsigned char *	dstBuffer,
		int &	len,
		int	quality = 75
	)

Parameters:

	srcBuffer	address of the image in memory
	width	width of image in pixels
	height	height of image in pixels
	bpp	number of bytes per pixel (1 or 3)
	dstBuffer	pointer to a buffer to buffer to return the compressed data. The function assumes that it was allocated with enough space to hold the compressed data
	len	returns the size of the compressed data. Initially this parameter should contain the size of the pre-allocated buffer
	quality	image quality as a percentage

Returns:

true or false whether the compressing was successfull or not

Definition at line 183 of file TeLibJpegWrapper.cpp.

Referenced by TeDecoderDatabase::putRasterBlock().

        {
                if (!srcBuffer || !dstBuffer || len<=0 )
                        return false;

                JSAMPROW row_pointer[1];        
                int row_stride = width*bpp;     

                struct jpeg_error_mgr jerr;
                struct jpeg_compress_struct cinfo;
                jpeg_create_compress(&cinfo);
                cinfo.err = jpeg_std_error(&jerr);
                if (bpp == 3)
                        cinfo.in_color_space = JCS_RGB; 
                else if (bpp == 1)
                        cinfo.in_color_space = JCS_GRAYSCALE; 
                cinfo.image_width = width;
                cinfo.image_height = height;
                cinfo.input_components = bpp;
                jpeg_set_defaults(&cinfo);
            jpeg_set_quality(&cinfo, quality, true);

                j_mem_dest(&cinfo,reinterpret_cast<void**>(&dstBuffer),reinterpret_cast<unsigned int*>(&len));
                jpeg_start_compress(&cinfo,true);
                while (cinfo.next_scanline < cinfo.image_height) 
                {
                        row_pointer[0] = &srcBuffer[cinfo.next_scanline * row_stride];
                        jpeg_write_scanlines(&cinfo, row_pointer, 1);
                }
                jpeg_finish_compress(&cinfo);
                jpeg_destroy_compress(&cinfo);
                return true;
        }

TL_DLL bool Jpeg::CompressToFile	(	unsigned char *	buffer,
		int	width,
		int	height,
		int	bpp,
		const std::string &	fileName,
		int	quality = 75
	)

Parameters:

	buffer	address of the buffer that contains the image in memory
	width	width of image in pixels
	height	height of image in pixels
	bpp	number of bytes per pixel (1 or 3)
	fileName	name of the compressed file
	quality	image quality as a percentage value

Returns:

true or false whether the compressing was successfull or not

bool Jpeg::CompressToFile	(	unsigned char *	buffer,
		int	width,
		int	height,
		int	bpp,
		const string &	fileName,
		int	quality = 75
	)

Definition at line 134 of file TeLibJpegWrapper.cpp.

Referenced by TeDecoderJPEG::clear(), and TeDecoderJPEG::init().

        {
                // check if input parameters are valid
                if (fileName.empty() || !buffer || (bpp != 1 && bpp != 3) )
                        return false;
                
                // create the destination file
                FILE* outfile = fopen(fileName.c_str(), "wb");
                if (outfile == 0) 
                        return false;

                // create access to source buffer as expected by jpeglib
                JSAMPROW row_pointer[1];        
                int row_stride = width*bpp;     

                // create compress structure
                struct jpeg_compress_struct cinfo;
                struct jpeg_error_mgr jerr;
                jpeg_create_compress(&cinfo);
                cinfo.err = jpeg_std_error(&jerr);

                // set the known parameters and default parameters
                if (bpp == 3)
                        cinfo.in_color_space = JCS_RGB; 
                else if (bpp == 1)
                        cinfo.in_color_space = JCS_GRAYSCALE; 
                cinfo.image_width = width;
                cinfo.image_height = height;
                cinfo.input_components = bpp;
                jpeg_set_defaults(&cinfo);
            jpeg_set_quality(&cinfo, quality, true);
                jpeg_stdio_dest(&cinfo, outfile);

                // decompress the data line by line
                jpeg_start_compress(&cinfo, true);
                while (cinfo.next_scanline < cinfo.image_height) 
                {
                        row_pointer[0] = &buffer[cinfo.next_scanline * row_stride];
                        jpeg_write_scanlines(&cinfo, row_pointer, 1);
                }

                // release structures
                jpeg_finish_compress(&cinfo);
                jpeg_destroy_compress(&cinfo);

                fclose(outfile);
                return true;
        }

TL_DLL bool Jpeg::DecompressBuffer	(	unsigned char *	srcBuffer,
		int	size,
		unsigned char *	dstBuffer,
		int &	width,
		int &	height,
		int &	bpp
	)

Parameters:

	srcBuffer	memory address containing jpeg compressed data
	size	size in bytes of the jpeg compressed data
	dstBuffer	pointer to a buffer to return the decompressed data. The function assumes that it was allocated with enough space to hold the decompressed data
	width	return the number of columns of the data
	height	return the number of lines of the data
	bpp	return the number of bytes per pixel

Returns:

true or false whether the decompressing was successfull or not

Definition at line 93 of file TeLibJpegWrapper.cpp.

Referenced by TeDecoderDatabase::getRasterBlock(), and TeDecoderDatabase::getSelectedRasterBlock().

        {
                if (!dstBuffer)
                        return false;

                struct jpeg_error_mgr jerr;
                struct jpeg_decompress_struct cinfo;

                cinfo.err = jpeg_std_error(&jerr);
                jpeg_create_decompress(&cinfo);

                j_mem_src (&cinfo, srcBuffer, size);

                jpeg_read_header(&cinfo,true);
                jpeg_start_decompress(&cinfo);
                
                width = cinfo.output_width;
                height = cinfo.output_height;
                bpp = cinfo.num_components;
                unsigned char* rowptr[1];
                while (cinfo.output_scanline < cinfo.output_height)
                {
                        rowptr[0] = &dstBuffer[cinfo.output_scanline*cinfo.output_width*cinfo.num_components];
                        if (rowptr[0] == 0)
                        {
                                jpeg_finish_decompress(&cinfo);
                                jpeg_destroy_decompress(&cinfo);
                                return false;
                        }
                        if (jpeg_read_scanlines(&cinfo, rowptr, 1) != 1)
                        {
                                jpeg_finish_decompress(&cinfo);
                                jpeg_destroy_decompress(&cinfo);
                                return false;
                        }
                }
                jpeg_finish_decompress(&cinfo);
                jpeg_destroy_decompress(&cinfo);
                return true;
        }

TL_DLL bool Jpeg::DecompressFile	(	const std::string &	fileName,
		unsigned char *	dstBuffer,
		int &	width,
		int &	height,
		int &	nChannels
	)

Parameters:

	fileName	name of the file
	dstBuffer	pointer to a buffer to return the decompressed data. The function assumes that it was allocated with enough space to hold the decompressed data
	width	returns the number of columns of the data
	height	returns the number of lines of the data
	nChannels	returns the number of bands, or channels, of the data

Returns:

true or false whether the decompressing was successfull or not

bool Jpeg::DecompressFile	(	const string &	fileName,
		unsigned char *	dstBuffer,
		int &	width,
		int &	height,
		int &	nChannels
	)

Definition at line 60 of file TeLibJpegWrapper.cpp.

Referenced by TeDecoderJPEG::init().

        {
                if (!dstBuffer || fileName.empty())
                        return false;

                FILE* infile;
                if ((infile = fopen(fileName.c_str(), "rb")) == 0) 
                        return false;
                
                struct jpeg_error_mgr jerr;
                struct jpeg_decompress_struct cinfo;
                cinfo.err = jpeg_std_error(&jerr);
                jpeg_create_decompress(&cinfo);
                jpeg_stdio_src(&cinfo, infile);
                jpeg_read_header(&cinfo, true);
                jpeg_start_decompress(&cinfo);

                width = cinfo.output_width; 
                height = cinfo.output_height;
                nChannels = cinfo.num_components;       

                unsigned char* rowptr[1];
                while (cinfo.output_scanline < cinfo.output_height)
                {
                        rowptr[0] = &dstBuffer[cinfo.output_scanline*cinfo.output_width*cinfo.num_components];
                        jpeg_read_scanlines(&cinfo, rowptr, 1);
                }
                jpeg_finish_decompress(&cinfo);
                jpeg_destroy_decompress(&cinfo);
                fclose(infile);
                return true;
        }       

TL_DLL bool Jpeg::ReadFileParams	(	const std::string &	fileName,
		int &	width,
		int &	height,
		int &	nChannels
	)

Parameters:

	fileName	name of the file
	width	return the number of columns of the data
	height	return the number of lines of the data
	nChannels	return the number of bands, or channels, of the data

Returns:

true or false whether the raster was imported successfully

bool Jpeg::ReadFileParams	(	const string &	fileName,
		int &	width,
		int &	height,
		int &	nChannels
	)

Definition at line 34 of file TeLibJpegWrapper.cpp.

Referenced by TeDecoderJPEG::TeDecoderJPEG().

        {
                if (fileName.empty())
                        return false;

                FILE* infile;
                if ((infile = fopen(fileName.c_str(), "rb")) == 0) 
                        return false;
                        
                struct jpeg_decompress_struct cinfo;
                struct jpeg_error_mgr jerr;
                cinfo.err = jpeg_std_error(&jerr);
                jpeg_create_decompress(&cinfo);

                jpeg_stdio_src(&cinfo, infile);
                jpeg_read_header(&cinfo, true);
                jpeg_calc_output_dimensions(&cinfo);
                
                width = cinfo.image_width;
                height = cinfo.image_height;
                nChannels = cinfo.num_components;
                jpeg_destroy_decompress(&cinfo);
                fclose(infile);
                return true;
        }

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