;# ====================================================================
;#
;# gifcat.pl: GIFファイル連結ライブラリ Ver1.50
;#
;# Copyright (c) 1997,1998 s-hasei@mtg.biglobe.ne.jp
;#
;# 著作権は放棄しませんが、自由に使用・改造・再配布可能です。
;# 改造版を再配布する際は、必ずファイル名を変更して、オリジナルを添付して
;# 配布してください。
;#
;# 基本的な使い方
;#    require "gifcat.pl";
;#    open(OUT, "> out.gif");
;#    binmode(OUT);    # MS-DOS や Windows の場合に必要です。
;#    print OUT &gifcat'gifcat("xx.gif", "yy.gif", "zz.gif");
;#    close(OUT);
;#
;# デバッグ用(GIFの解析出力)
;#    require "gifcat.pl";
;#    &gifcat'gifprint("xx.gif", "yy.gif", "zz.gif");
;#
;# 制限事項
;#    アニメGIFは連結できません。
;#    大きさの異なるGIFファイルは連結できません。
;#
;# 最新版入手先
;#    http://www2e.biglobe.ne.jp/~s-hasei/cgi-bin/gifcat.pl
;#
;# 更新履歴:
;#    1997.05.03 初版。
;#    1997.05.10 スペルミス修正。
;#    1997.05.29 サイズの異なるカラーテーブルに対応。
;#    1997.07.07 エラー発生時にexit()しないように修正。
;#    1998.05.05 Trailerを持たないGIFファイルを連結できないバグを修正。
;#    1998.05.05 横幅が256を超えるGIFの出力ができないバグを修正。
;#    1998.05.05 gifprint()で連結結果を出力しないように修正。
;#    1998.05.10 連結できないGIF画像があるというバグを修正。
;#    1998.08.20 Ver1.50 変数の初期化を行うように修正。
;#    1998.08.20 Ver1.50 透過GIFに対応。
;#
;# ====================================================================

package gifcat;

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

;# =====================================================
;# gifcat'gifcat() - get a concatenated GIF image.
;# =====================================================
sub gifcat {
    $Gif = 0;
    $useLocalColorTable = 0;
    @files = @_;
    for $file (@files) {
        ($dev,$ino,$mode,$nlink,$uid,$gif,$rdev,
            $size,$atime,$mtime,$ctime,$blksize,$blocks)
                = stat($file);
        open(IN, "$file");
        binmode(IN);
        sysread(IN, $buf, $size);
        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 = 0; $i < $Gif; $i++) {
        $GifImage .= pack("CCC", 0x21, 0xf9, 0x04);
        $GifImage .= pack("C", $PackedFields23 | $TransparentColorFlag[$i]);
        $GifImage .= pack("CC", 0x00, 0x00);
        $GifImage .= pack("C", $TransparentColorIndex[$i]);
        $GifImage .= pack("C", 0x00);
        $GifImage .= pack("C", 0x2c);
        $n = $ImageWidth * $i;
        $GifImage .= pack("C", $n & 0x00ff);
        $GifImage .= pack("C", ($n & 0xff00) >> 8);
        $GifImage .= pack("CC", 0x00, 0x00);
        $GifImage .= pack("C", $ImageWidth & 0x00ff);
        $GifImage .= pack("C", ($ImageWidth & 0xff00) >> 8);
        $GifImage .= pack("C", $ImageHeight & 0x00ff);
        $GifImage .= pack("C", ($ImageHeight & 0xff00) >> 8);
        if ($useLocalColorTable) {
            $PackedFields20[$i] |= 0x80;
            $PackedFields20[$i] &= ~0x07;
            $PackedFields20[$i] |= ($PackedFields18[$i] & 0x07);
            $GifImage .= pack("C", $PackedFields20[$i]);
            $GifImage .= $globalColorTable[$i];
        } else {
            $GifImage .= pack("C", $PackedFields20[$i]);
        }
        $GifImage .= pack("C", $LzwMinimumCodeSize[$i]);
        $GifImage .= $ImageData[$i];
    }
    $GifImage .= pack("C", 0x3b);

}

;# =====================================
;# GifHeader
;# =====================================
sub GifHeader {
    $Signature = substr($buf, $cnt, 3); $cnt += 3;
    $Version   = substr($buf, $cnt, 3); $cnt += 3;
    $LogicalScreenWidth
            = ord(substr($buf, $cnt + 0, 1))
            + ord(substr($buf, $cnt + 1, 1)) * 256; $cnt += 2;
    $LogicalScreenHeight
            = ord(substr($buf, $cnt + 0, 1))
            + ord(substr($buf, $cnt + 1, 1)) * 256; $cnt += 2;
    $PackedFields18[$Gif]   = ord(substr($buf, $cnt, 1)); $cnt++;
    $GlobalColorTableFlag   = ($PackedFields18[$Gif] & 0x80) >> 7;
    $ColorResolution        = (($PackedFields18[$Gif] & 0x70) >> 4) + 1;
    $SortFlag               = ($PackedFields18[$Gif] & 0x08) >> 3;
    $SizeOfGlobalColorTable = 2 ** (($PackedFields18[$Gif] & 0x07) + 1);
    $BackgroundColorIndex   = ord(substr($buf, $cnt, 1)); $cnt++;
    $PixelAspectRatio       = ord(substr($buf, $cnt, 1)); $cnt++;
    if ($GlobalColorTableFlag) {
        $GlobalColorTable 
            = substr($buf, $cnt, $SizeOfGlobalColorTable * 3);
        $cnt += $SizeOfGlobalColorTable * 3;
    }

    $logicalScreenWidth += $LogicalScreenWidth;
    if ($logicalScreenHeight < $LogicalScreenHeight) {
        $logicalScreenHeight = $LogicalScreenHeight;
    }
    if ($GlobalColorTableFlag) {
        $globalColorTable[$Gif] = $GlobalColorTable;
        if ($Gif > 0) {
            if ($GlobalColorTable ne $globalColorTable[$Gif - 1]) {
                $useLocalColorTable = 1;
            }
        }
    }

    if ($pflag) {
        printf("=====================================\n");
        printf("GifHeader\n");
        printf("=====================================\n");
        printf("Signature:                     %s\n", $Signature);
        printf("Version:                       %s\n", $Version);
        printf("Logical Screen Width:          %d\n", $LogicalScreenWidth);
        printf("Logical Screen Height:         %d\n", $LogicalScreenHeight);
        printf("Global Color Table Flag:       %d\n", $GlobalColorTableFlag);
        printf("Color Resolution:              %d\n", $ColorResolution);
        printf("Sort Flag:                     %d\n", $SortFlag);
        printf("Size of Global Color Table:    %d\n", $SizeOfGlobalColorTable);
        printf("Background Color Index:        %d\n", $BackgroundColorIndex);
        printf("Pixel Aspect Ratio:            %d\n", $PixelAspectRatio);
        printf("Global Color Table:            ...\n");
    }
}

;# =====================================
;# Image Block
;# =====================================
sub ImageBlock {
    $ImageSeparator    = ord(substr($buf, $cnt, 1)); $cnt++;
    $ImageLeftPosition = ord(substr($buf, $cnt, 1))
               + ord(substr($buf, $cnt + 1, 1)) * 256; $cnt += 2;
    $ImageTopPosition  = ord(substr($buf, $cnt, 1))
               + ord(substr($buf, $cnt + 1, 1)) * 256; $cnt += 2;
    $ImageWidth        = ord(substr($buf, $cnt, 1))
               + ord(substr($buf, $cnt + 1, 1)) * 256; $cnt += 2;
    $ImageHeight       = ord(substr($buf, $cnt, 1))
               + ord(substr($buf, $cnt + 1, 1)) * 256; $cnt += 2;
    $PackedFields20[$Gif]  = ord(substr($buf, $cnt, 1)); $cnt++;
    $LocalColorTableFlag   = ($PackedFields20[$Gif] & 0x80) >> 7;
    $InterlaceFlag         = ($packedFields20[$Gif] & 0x40) >> 6;
    $SortFlag              = ($PackedFields20[$Gif] & 0x20) >> 5;
    $Reserved              = ($PackedFields20[$Gif] & 0x18) >> 3;
    $SizeOfLocalColorTable = 2 ** (($PackedFields20[$Gif] & 0x07) + 1);
    if ($LocalColorTableFlag) {
        $cnt += $SizeOfLocalColorTable * 3;
    }
    $LzwMinimumCodeSize[$Gif] = ord(substr($buf, $cnt, 1)); $cnt++;
    $ImageData[$Gif] = &DataSubBlock();

    if ($pflag) {
        printf("=====================================\n");
        printf("Image Block\n");
        printf("=====================================\n");
        printf("Image Separator:               0x%02x\n", $ImageSeparator);
        printf("Image Left Position:           %d\n", $ImageLeftPosition);
        printf("Image Top Position:            %d\n", $ImageTopPosition);
        printf("Image Width:                   %d\n", $ImageWidth);
        printf("Image Height:                  %d\n", $ImageHeight);
        printf("Local Color Table Flag:        %d\n", $LocalColorTableFlag);
        printf("Interlace Flag:                %d\n", $InterlaceFlag);
        printf("Sort Flag:                     %d\n", $SortFlag);
        printf("Reserved:                      --\n");
        printf("Size of Local Color Table:     %d\n", $SizeOfLocalColorTable);
        printf("Local Color Table:             ...\n");
        printf("LZW Minimum Code Size:         %d\n", $LzwMinimumCodeSize[$Gif]);
        printf("Image Data:                    ...\n");
        printf("Block Terminator:              0x00\n");
    }
}

;# =====================================
;# Graphic Control Extension
;# =====================================
sub GraphicControlExtension {
    $ExtensionIntroducer   = ord(substr($buf, $cnt, 1)); $cnt++;
    $GraphicControlLabel   = ord(substr($buf, $cnt, 1)); $cnt++;
    $BlockSize             = ord(substr($buf, $cnt, 1)); $cnt++;
    $PackedFields23        = ord(substr($buf, $cnt, 1)); $cnt++;
    $Reserved              = ($PackedFields23 & 0xe0) >> 5;
    $DisposalMethod        = ($PackedFields23 & 0x1c) >> 5;
    $UserInputFlag         = ($PackedFields23 & 0x02) >> 1;
    $TransparentColorFlag[$Gif]  = $PackedFields23 & 0x01;
    $DelayTime             = ord(substr($buf, $cnt, 1))
                   + ord(substr($buf, $cnt+1, 1)) * 256; $cnt += 2;
    $TransparentColorIndex[$Gif] = ord(substr($buf, $cnt, 1)); $cnt++;
    $BlockTerminator       = ord(substr($buf, $cnt, 1)); $cnt++;

    if ($pflag) {
        printf("=====================================\n");
        printf("Graphic Control Extension\n");
        printf("=====================================\n");
        printf("Extension Introducer:          0x%02x\n", $ExtensionIntroducer);
        printf("Graphic Control Label:         0x%02x\n", $GraphicControlLabel);
        printf("Block Size:                    %d\n", $BlockSize);
        printf("Reserved:                      --\n");
        printf("Disposal Method:               %d\n", $DisposalMethod);
        printf("User Input Flag:               %d\n", $UserInputFlag);
        printf("Transparent Color Flag:        %d\n", $TransparentColorFlag[$Gif]);
        printf("Delay Time:                    %d\n", $DelayTime);
        printf("Transparent Color Index:       %d\n", $TransparentColorIndex[$Gif]);
        printf("Block Terminator:              0x00\n");
    }
}

;# =====================================
;# Comment Extension
;# =====================================
sub CommentExtension {
    $ExtensionIntroducer   = ord(substr($buf, $cnt, 1)); $cnt++;
    $CommentLabel          = ord(substr($buf, $cnt, 1)); $cnt++;
    &DataSubBlock();

    if ($pflag) {
        printf("=====================================\n");
        printf("Comment Extension\n");
        printf("=====================================\n");
        printf("Extension Introducer:          0x%02x\n", $ExtensionIntroducer);
        printf("Comment Label:                 0x%02x\n", $CommentLabel);
        printf("Comment Data:                  ...\n");
        printf("Block Terminator:              0x%02x\n", $BlockTerminator);
    }
}

;# =====================================
;# Plain Text Extension
;# =====================================
sub PlainTextExtension {
    $ExtensionIntroducer  = ord(substr($buf, $cnt, 1)); $cnt++;
    $PlainTextLabel       = ord(substr($buf, $cnt, 1)); $cnt++;
    $BlockSize            = ord(substr($buf, $cnt, 1)); $cnt++;
    $TextGridLeftPosition = ord(substr($buf, $cnt, 1))
                  + ord(substr($buf, $cnt + 1, 1)) * 256; $cnt += 2;
    $TextGridTopPosition  = ord(substr($buf, $cnt, 1))
                  + ord(substr($buf, $cnt + 1, 1)) * 256; $cnt += 2;
    $TextGridWidth        = ord(substr($buf, $cnt, 1))
                  + ord(substr($buf, $cnt + 1, 1)) * 256; $cnt += 2;
    $TextGridHeight       = ord(substr($buf, $cnt, 1))
                  + ord(substr($buf, $cnt + 1, 1)) * 256; $cnt += 2;
    $CharacterCellWidth   = ord(substr($buf, $cnt, 1)); $cnt++;
    $CharacterCellHeight  = ord(substr($buf, $cnt, 1)); $cnt++;
    $TextForegroundColorIndex = ord(substr($buf, $cnt, 1)); $cnt++;
    $TextBackgroundColorIndex = ord(substr($buf, $cnt, 1)); $cnt++;
    &DataSubBlock();

    if ($pflag) {
        printf("=====================================\n");
        printf("Plain Text Extension\n");
        printf("=====================================\n");
        printf("Extension Introducer:        0x%02x\n", $ExtensionIntroducer);
        printf("Plain Text Label:            0x%02x\n", $PlainTextLabel);
        printf("Block Size:                  0x%02x\n", $BlockSize);
        printf("Text Grid Left Position:     %d\n", $TextGridLeftPosition);
        printf("Text Grid Top Position:      %d\n", $TextGridTopPosition);
        printf("Text Grid Width:             %d\n", $TextGridWidth);
        printf("Text Grid Height:            %d\n", $TextGridHeight);
        printf("Text Foreground Color Index: %d\n", $TextForegroundColorIndex);
        printf("Text Background Color Index: %d\n", $TextBackgroundColorIndex);
        printf("Plain Text Data:             ...\n");
        printf("Block Terminator:            0x00\n");
    }
}

;# =====================================
;# Application Extension
;# =====================================
sub ApplicationExtension {
    $ExtensionIntroducer           = ord(substr($buf, $cnt, 1)); $cnt++;
    $ExtentionLabel                = ord(substr($buf, $cnt, 1)); $cnt++;
    $BlockSize                     = ord(substr($buf, $cnt, 1)); $cnt++;
    $ApplicationIdentifire         = substr($buf, $cnt, 8); $cnt += 8;
    $ApplicationAuthenticationCode = substr($buf, $cnt, 3); $cnt += 3;
    &DataSubBlock();

    if ($pflag) {
        printf("=====================================\n");
        printf("Application Extension\n");
        printf("=====================================\n");
        printf("Extension Introducer:          0x%02x\n",
            $ExtensionIntroducer);
        printf("Extension Label:               0x%02x\n",
            $PlainTextLabel);
        printf("Block Size:                    0x%02x\n",
            $BlockSize);
        printf("Application Identifire:        ...\n");
        printf("ApplicationAuthenticationCode: ...\n");
        printf("Block Terminator:              0x00\n");
    }
}

;# =====================================
;# Trailer
;# =====================================
sub Trailer {
    $cnt++;

    if ($pflag) {
        printf("=====================================\n");
        printf("Trailer\n");
        printf("=====================================\n");
        printf("Trailer:                       0x3b\n");
        printf("\n");
    }
}

;# =====================================
;# Data Sub Block
;# =====================================
sub DataSubBlock {
    local($n, $from);
    $from = $cnt;
    while ($n = ord(substr($buf, $cnt, 1))) {
        $cnt++;
        $cnt += $n;
    }
    $cnt++;
    return(substr($buf, $from, $cnt - $from));
}

1;