/GifMagic/Encoder.php

<?php
/*
 * Copyright (c) 2011, webvariants GbR, http://www.webvariants.de
 *
 * This file is released under the terms of the MIT license. You can find the
 * complete text in the attached LICENSE file or online at:
 *
 * http://www.opensource.org/licenses/mit-license.php
 *
 * based on GIFEncoder Version 3.0 by Lรกszlรณ Zsidi
 * http://www.phpclasses.org/package/3163-PHP-Generate-GIF-animations-from-a-set-of-GIF-images.html
 * http://www.phpclasses.org/package/3234-PHP-Split-GIF-animations-into-multiple-images.html
 * http://www.gifs.hu
 */

/**
 * @author robert.koppsieker@webvariants.de
 */
class GifMagic_Encoder {
	private $result = 'GIF89a'; // GIF header 6 bytes

	private $buffers = array();
	private $OFS = array();
	private $SIG =  0;
	private $LOP =  0;
	private $DIS =  2;
	private $COL = -1;
	private $IMG = -1;

	private $ERR = array(
		'ERR01' => 'Source is not a GIF image!',
		'ERR02' => 'Unintelligible flag',
		'ERR03' => 'Does not make animation from animated GIF source',
	);

	public function __construct(array $sources, array $result_dly, $loop, $disposables,
		$red, $green, $blue, $offsets, $sourceMode) {

		$this->LOP = $loop === false ? false : (($loop > -1) ? $loop : 0);
		$this->COL = ($red > -1 && $green > -1 && $blue > -1) ?
		             ($red | ($green << 8) | ($blue << 16)) : -1;

		$sourceMode = strtolower($sourceMode);

		if (!in_array($sourceMode, array('url', 'bin'))) {
			throw new GifMagic_Exception($this->ERR['ERR02']." ($sourceMode)", 2);
		}

		for ($i = 0; $i < count ($sources); $i++) {
			if ($sourceMode === 'url') {
				$this->buffers[] = file_get_contents($sources[$i]);
			}
			else {
				$this->buffers[] = $sources [$i];
			}

			if (strlen($this->buffers[$i]) < 6) {
				throw new GifMagic_Exception('Invalid file given (file smaller than GIF signature).');
			}

			$sig = substr($this->buffers[$i], 0, 6);

			if ($sig !== 'GIF87a' && $sig !== 'GIF89a') {
				throw new GifMagic_Exception($this->ERR['ERR01'], 1);
			}

			for ($j = $this->getLocalsStrLength($i), $k = true; $k; $j++) {
				switch ($this->buffers[$i][$j]) {
					case '!':
						if ((substr($this->buffers[$i], ($j + 3), 8)) === 'NETSCAPE') {
							throw new GifMagic_Exception(sprintf('%s (%d source)', $this->ERR['ERR03'], $i+1), 3);
						}
						break;

					case ';':
						$k = false;
						break;
				}
			}
		}

		if (!is_array($offsets)) {
			$offsets = array();
		}

		for ($i = 0; $i < count($this->buffers); $i++) {
			if (!isset($disposables[$i])) $disposables[$i] = $this->DIS;
			else $disposables[$i] = ($disposables[$i] > -1) ? (($disposables[$i] < 3) ? $disposables[$i] : 3) : 2;

			if (!isset($offsets[$i])) $offsets[$i] = 0;
		}

		if (count($offsets) > 1) {
			$this->SIG = 1;
			$this->OFS = $offsets;
		}

		$this->addHeader();

		for ($i = 0; $i < count($this->buffers); $i++) {
			$this->addFrames($i, $result_dly [$i], $disposables[$i]);
		}

		$this->addFooter();
	}

	private function addHeader() {
		$cmap = 0;

		if (ord($this->buffers[0][10]) & 0x80) {
			$cmap = $this->getColorTableLength(0);

			$this->result .= substr($this->buffers[0],  6, 7);
			$this->result .= substr($this->buffers[0], 13, $cmap);

			if ($this->LOP !== false) {
				$this->result .= "!\377\13NETSCAPE2.0\3\1".$this->intToWord($this->LOP)."\0";
			}
		}
	}

	/**
	 *
	 * @param int     $delay             delay in seconds to next image
	 * @param int     $disposal          disposal method type (0-7)
	 * @param int     $transpColorIndex  color index for transparency
	 * @return string in hex code
	 */
	private function getGraphicalControlExtension($delay, $disposal, $transpColorIndex = null) {
		$transpFlag = 0;
		if (!is_int($transpColorIndex) || $transpColorIndex < 0) $transpColorIndex = 0;
		else $transpFlag = 1;

		return "\x21"                    // extension introducer (always 21)
		     . "\xF9"                    // graphic control label (F9 means graphic control extension)
		     . "\x04"                    // block size (fixed value 4)
		     . chr(                      // packed fields
		           ($disposal << 2)         // disposal method
		         + $transpFlag              // transparency flag
		     )
		     . chr(($delay >> 0) & 0xFF) // delay time
		     . chr(($delay >> 8) & 0xFF) // delay time
		     . chr($transpColorIndex)    // transparent color index
		     . "\x0";                    // block terminator (always zero)
	}

	private function getColorLength($imageNumber) {
		return 2 << (ord($this->buffers[$imageNumber][10]) & 0x07);
	}

	private function getColorTableLength($imageNumber) {
		return 3 * $this->getColorLength($imageNumber);
	}

	private function getLocalsStrLength($imageNumber) {
		return 13 + $this->getColorTableLength($imageNumber);
	}

	private function getXYPadding($i, $Locals_ext, $Locals_img, $Locals_rgb, $Locals_tmp, $local=true) {
		if ($this->SIG == 1) {
			$Locals_img[1] = chr( $this->OFS[$i][0] & 0xFF);
			$Locals_img[2] = chr(($this->OFS[$i][0] & 0xFF00) >> 8);
			$Locals_img[3] = chr( $this->OFS[$i][1] & 0xFF);
			$Locals_img[4] = chr(($this->OFS[$i][1] & 0xFF00) >> 8);
		}

		$byte  = ord($Locals_img[9]);
		$byte |= 0x80;
		$byte &= 0xF8;

		if ($local) $byte |= (ord($this->buffers[$i][10]) & 0x07);
		else        $byte |= (ord($this->buffers[0] [10]) & 0x07);

		$Locals_img[9] = chr($byte);

		return $Locals_ext.$Locals_img.$Locals_rgb.$Locals_tmp;
	}

	private function addFrames($i, $d, $disposal) {
		$Locals_str = $this->getLocalsStrLength($i);

		$Locals_end = strlen($this->buffers[$i]) - $Locals_str - 1;
		$Locals_tmp = substr($this->buffers[$i], $Locals_str, $Locals_end);

		$Global_len = $this->getColorLength(0);
		$Locals_len = $this->getColorLength($i);

		$Global_rgb = substr($this->buffers[0], 13, $this->getColorTableLength(0));
		$Locals_rgb = substr($this->buffers[$i], 13, $this->getColorTableLength($i));

		// first frame
		$transpColorIndex = ord(substr($this->buffers[$i], $Locals_str+6, 1));
		$Locals_ext = $this->getGraphicalControlExtension($d, $disposal, $transpColorIndex);

//		if ($this->COL > -1 && ord($this->buffers[$i][10]) & 0x80) {
//			print 'maximum color index: '.$this->getColorLength($i).'<br>';
//			for ($j = 0; $j < $this->getColorLength($i); $j++) {
//
//				if (ord($Locals_rgb[3 * $j + 0]) == (($this->COL >> 16) & 0xFF)
//				 && ord($Locals_rgb[3 * $j + 1]) == (($this->COL >>  8) & 0xFF)
//				 && ord($Locals_rgb[3 * $j + 2]) == (($this->COL >>  0) & 0xFF)) {
//
//					$Locals_ext = $this->getGraphicalControlExtension($d, $disposal, $j);
//					break;
//				}
//			}
//			// hack to get index 1 transparent
//			if ($i > 0) $Locals_ext = $this->getGraphicalControlExtension($d, $disposal, 1);
//		}

		switch ($Locals_tmp[0]) {
			case '!':
				$Locals_img = substr($Locals_tmp, 8, 10);
				$Locals_tmp = substr($Locals_tmp, 18, strlen($Locals_tmp) - 18);
				break;

			case ',':
				$Locals_img = substr($Locals_tmp, 0, 10);
				$Locals_tmp = substr($Locals_tmp, 10, strlen($Locals_tmp) - 10);
				break;
		}

		if (ord($this->buffers[$i][10]) & 0x80 && $this->IMG > -1) {

			// global and local color table have same length
			if ($Global_len == $Locals_len) {
				// global and local color table are equal
				if ($Global_rgb === $Locals_rgb) {
					$this->result .= $Locals_ext.$Locals_img.$Locals_tmp;
				}
				else {
					$this->result .= $this->getXYPadding($i, $Locals_ext, $Locals_img, $Locals_rgb, $Locals_tmp, false);
				}
			}
			// special local color table
			else {
				$this->result .= $this->getXYPadding($i, $Locals_ext, $Locals_img, $Locals_rgb, $Locals_tmp);
			}
		}
		else {
			$this->result .= $Locals_ext.$Locals_img.$Locals_tmp;
		}

		$this->IMG = 1;
	}

	private function addFooter() {
		$this->result .= ';';
	}

	private function intToWord($int) {
		return chr($int & 0xFF).chr(($int >> 8) & 0xFF);
	}

	public function getAnimation() {
		return $this->result;
	}
}