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/*
//
// png.c
//
// PNG (Portable Network Graphics) support functions
//
// By Rev. Bob, 1999 - derived from gif.c by Jim Nelson
//
// gif.c Copyright (c) 1995-96 Jim Nelson. Permission to distribute
// granted by the author. No warranties are made on the fitness of this
// source code.
//
*/
#include "htp.h"
BOOL PngFormatFound(FILE *file)
{
BYTE header[8];
/* move to BOF */
if(fseek(file, 0, SEEK_SET) != 0)
{
DEBUG_PRINT(("unable to seek to start of PNG file"));
return FALSE;
}
/* read first eight bytes, looking for PNG header + version info */
if(fread(header, 1, 8, file) != 8)
{
DEBUG_PRINT(("could not read PNG image file header"));
return FALSE;
}
/* is this a PNG file? */
if(memcmp(header, "\211PNG\r\n\032\n", 8) == 0)
{
if(fseek(file, 12, SEEK_SET) != 0)
{
DEBUG_PRINT(("unable to seek to IHDR block of PNG file"));
return FALSE;
}
if(fread(header, 1, 4, file) != 4)
{
DEBUG_PRINT(("could not read PNG image IHDR signature"));
return FALSE;
}
if(memcmp(header, "IHDR", 4) == 0)
{
/* PNG signature and IHDR block found, must be good */
return TRUE;
}
}
/* not a PNG file */
return FALSE;
}
/* Modify parms here and in png.h - must use 4-byte integers! */
BOOL PngReadDimensions(FILE *file, DWORD *height, DWORD *width)
{
/* PNG uses MSB LSB (B3 B2 B1 B0) notation - most significant first */
BYTE buff[8];
/* move to the image size position (+16) in the file header */
if(fseek(file, 16, SEEK_SET) != 0)
{
DEBUG_PRINT(("unable to seek to start of PNG file"));
return FALSE;
}
/* read the width and height, byte by byte */
/* this gets around machine endian problems while retaining the */
/* fact that PNG uses MSB LSB (big-endian) notation */
if(fread(buff, 1, 8, file) != 8)
{
return FALSE;
}
*width = MAKE_DWORD(buff[0], buff[1], buff[2], buff[3]);
*height = MAKE_DWORD(buff[4], buff[5], buff[6], buff[7]);
return TRUE;
}
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