学步园

附VC编译的源代码：下载地址

BOOL BmpToJpg( int nWidth, int nHeight, int nPixelBytes, BYTE* byBmpData, BYTE** byJpgData, unsigned long* nSize )
{
	BOOL bResult = FALSE;
	
	jpeg_compress_struct jCompress;
	jpeg_error_mgr       jErrorMgr;
	
	jCompress.err = jpeg_std_error( &jErrorMgr );
	
	jpeg_create_compress( &jCompress );
	
	jpeg_mem_dest( &jCompress, byJpgData, nSize );
	
	jCompress.image_width      = nWidth;
	jCompress.image_height     = nHeight;
	jCompress.input_components = nPixelBytes;
	jCompress.in_color_space   = JCS_UNKNOWN;
	
	jpeg_set_defaults( &jCompress );
	jpeg_set_quality ( &jCompress, 70, true );
	
	jpeg_start_compress( &jCompress, true );
	
	int nLineWidth = nWidth * nPixelBytes;
	
	for ( int i = 0; i < nHeight; ++i )
	{
		BYTE* lpJpgBits = byBmpData + ( nHeight - i - 1 ) * nLineWidth;
		
		JSAMPROW row_pointer = lpJpgBits;
		
		jpeg_write_scanlines( &jCompress, &row_pointer, 1 );
	}
	
	jpeg_finish_compress( &jCompress );
	jpeg_destroy_compress( &jCompress );
	
	return bResult;
}

BOOL JpgToBmp( BYTE* byJpgData, BYTE* byBmpData, unsigned long* nSize )
{
	BOOL bResult = FALSE;
	
	jpeg_decompress_struct jDecompress;
	jpeg_error_mgr         jErrorMgr;
	
	jDecompress.err = jpeg_std_error( &jErrorMgr );
	
	jpeg_create_decompress( &jDecompress );
	
	jpeg_mem_src( &jDecompress, byJpgData, *nSize );
	
	jpeg_read_header( &jDecompress, true );
	
	jpeg_start_decompress( &jDecompress );
	
	int nHeight    = jDecompress.output_height;
	int nLineWidth = jDecompress.output_components * jDecompress.output_width;
	
	for ( int i = 0; i < nHeight; ++i )
	{
		BYTE* lpBmBits = byBmpData + ( nHeight - i - 1 ) * nLineWidth;
		
		jpeg_read_scanlines( &jDecompress, &lpBmBits, 1 );
	}
	
	jpeg_finish_decompress( &jDecompress );
	jpeg_destroy_decompress( &jDecompress );

	*nSize = nLineWidth * nHeight;

	return bResult;
}