/**
* Resize the gif by a ratio. The height and width will be scaled in proportion, maintaining the aspect ratio.
* Example: A ratio of 0.5 will half the size, a ratio of 2 will double it.
*
* @param string $srcFile
* @param string $dstFile the destination file. This will get overwritten if it already exists.
* @param float $ratio
*
* @throws Exception
*/
public static function ResizeByRatio($srcFile, $dstFile, $ratio)
{
$fh = new FileHandler();
$fhW = new FileHandler();
try {
$fh->openFile($srcFile);
} catch (Exception $e) {
throw $e;
}
$header = new Header($fh);
if ($header->signature !== "GIF" && $header->version !== "87a" && $header->version !== "89a") {
$fh->closeFile();
throw new Exception("Not a gif file.");
}
try {
if (is_file($dstFile)) {
unlink($dstFile);
}
$fhW->openFile($dstFile, true);
} catch (Exception $e) {
throw $e;
}
$fhW->writeData("GIF89a");
$lsd = new LogicalScreenDescriptor($fh);
$lsd->resize($ratio);
$lsd->encodeToFile($fhW);
self::processGifStream($fh, $fhW, $ratio, $lsd);
$fh->closeFile();
$fhW->closeFile();
}
/**
* @param string $dstPath
* @param int $frameCount
* @param LogicalScreenDescriptor $lsd
* @param AbstractExtensionBlock $aeb
*
* @throws Exception
*/
private static function writeFrame($dstPath, &$frameCount, $lsd, $aeb)
{
$frameCount++;
if ($dstPath !== null) {
$dstFileName = $dstPath . str_pad(strval($frameCount), 3, "0", STR_PAD_LEFT) . ".gif";
$fhW = new FileHandler();
$fhW->openFile($dstFileName, true);
$fhW->writeData("GIF89a");
$lsd->encodeToFile($fhW);
$aeb->encodeToFile($fhW);
$fhW->writeData(";");
$fhW->closeFile();
}
}