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examples/cgi/WwwCounter/gifcat.pl  view on Meta::CPAN

package gifcat;

$pflag = 0;					# print flag

;# =====================================================
;# gifcat'gifprint() - print out GIF diagnostics.
;# =====================================================
sub gifprint {
	$pflag = 1;
	&gifcat(@_);
	$pflag = 0;
}

;# =====================================================
;# gifcat'gifcat() - get a concatenated GIF image.
;# =====================================================
sub gifcat {
	@files = @_;
	$Gif = 0;
	$leftpos = 0;
	$logicalScreenWidth = 0;
	$logicalScreenHeight = 0;
	$useLocalColorTable = 0;
	
	foreach $file (@files) {
		$size = -s $file;
		open(IN, "$file") || return("ERROR");
		binmode(IN);
		read(IN, $buf, $size) || return("ERROR");
		close(IN);

		$cnt = 0;
		&GifHeader();
		while (1) {
			$x1 = ord(substr($buf, $cnt, 1));
			if ($x1 == 0x2c) {
				&ImageBlock();
			} elsif ($x1 == 0x21) {
				$x2 = ord(substr($buf, $cnt + 1, 1));
				if ($x2 == 0xf9) {
					&GraphicControlExtension();
				} elsif ($x2 == 0xfe) {
					&CommentExtension();
				} elsif ($x2 == 0x01) {
					&PlainTextExtension();
				} elsif ($x2 == 0xff) {
					&ApplicationExtension();
				} else {
					return("ERROR");
				}
			} elsif ($x1 == 0x3b) {
				&Trailer();
				last;
			} elsif ($cnt == $size) {
				last;
			} else {
				return("ERROR");
			}
		}

		undef($buf);
		$Gif++;
	}
	if ($pflag == 1) {
		return;
	}

	$GifImage = "GIF89a";
	$GifImage .= pack("C", $logicalScreenWidth & 0x00ff);
	$GifImage .= pack("C", ($logicalScreenWidth & 0xff00) >> 8);
	$GifImage .= pack("C", $logicalScreenHeight & 0x00ff);
	$GifImage .= pack("C", ($logicalScreenHeight & 0xff00) >> 8);
	if ($useLocalColorTable) {
		$PackedFields18[0] &= ~0x80;
	}
	$GifImage .= pack("C", $PackedFields18[0]);
	$GifImage .= pack("C", $BackgroundColorIndex);
	$GifImage .= pack("C", $PixelAspectRatio);
	if ($useLocalColorTable == 0) {
		$GifImage .= $globalColorTable[0];
	}
	for ($i = -1; $i < $Gif; $i++) {
		$j = ($i == -1) ? 0 : $i;
		$GifImage .= pack("CCC", 0x21, 0xf9, 0x04);
		$GifImage .= pack("C", $PackedFields23 | $TransparentColorFlag[$j]);
		$GifImage .= pack("CC", 0x00, 0x00);
		$GifImage .= pack("C", $TransparentColorIndex[$j]);
		$GifImage .= pack("C", 0x00);
		$GifImage .= pack("C", 0x2c);
		$n = $leftpos;
		$leftpos += ($i == -1) ? 0 : $ImageWidth[$j];
		$GifImage .= pack("C", $n & 0x00ff);
		$GifImage .= pack("C", ($n & 0xff00) >> 8);
		$GifImage .= pack("CC", 0x00, 0x00);
		$GifImage .= pack("C", $ImageWidth[$j] & 0x00ff);
		$GifImage .= pack("C", ($ImageWidth[$j] & 0xff00) >> 8);
		$GifImage .= pack("C", $ImageHeight & 0x00ff);
		$GifImage .= pack("C", ($ImageHeight & 0xff00) >> 8);
		if ($useLocalColorTable) {
			$PackedFields20[$j] |= 0x80;
			$PackedFields20[$j] &= ~0x07;
			$PackedFields20[$j] |= ($PackedFields18[$j] & 0x07);
			$GifImage .= pack("C", $PackedFields20[$j]);
			$GifImage .= $globalColorTable[$j];
		} else {
			$GifImage .= pack("C", $PackedFields20[$j]);
		}
		$GifImage .= pack("C", $LzwMinimumCodeSize[$j]);
		$GifImage .= $ImageData[$j];
	}
	$GifImage .= pack("C", 0x3b);

}

;# =====================================
;# GifHeader
;# =====================================
sub GifHeader {
	$Signature = substr($buf, $cnt, 3); $cnt += 3;
	$Version   = substr($buf, $cnt, 3); $cnt += 3;
	$LogicalScreenWidth