PHPを使って、画像のファイルを切り出し、縮小、サムネイルする方法

2014年7月25日

PHPコード：
処理関数の定義
function imagecropper($source_path, $target_width, $target_height)
{
$source_info = getimagesize($source_path);
$source_width = $source_info[0];
$source_height = $source_info[1];
$source_mime = $source_info['mime’];
$source_ratio = $source_height / $source_width;
$target_ratio = $target_height / $target_width;

//元画像が高すぎる
if ($source_ratio > $target_ratio)
{
$cropped_width = $source_width;
$cropped_height = $source_width * $target_ratio;
$source_x = 0;
$source_y = ($source_height – $cropped_height) / 2;
}
// 元画像が広すぎる
elseif ($source_ratio < $target_ratio)
{
$cropped_width = $source_height / $target_ratio;
$cropped_height = $source_height;
$source_x = ($source_width – $cropped_width) / 2;
$source_y = 0;
}
// 画像が適度
else
{
$cropped_width = $source_width;
$cropped_height = $source_height;
$source_x = 0;
$source_y = 0;
}

switch ($source_mime)
{
case 'image/gif’:
$source_image = imagecreatefromgif($source_path);
break;

case 'image/jpeg’:
$source_image = imagecreatefromjpeg($source_path);
break;

case 'image/png’:
$source_image = imagecreatefrompng($source_path);
break;

default:
return false;
break;
}

$target_image = imagecreatetruecolor($target_width, $target_height);
$cropped_image = imagecreatetruecolor($cropped_width, $cropped_height);

// 画像の切り出し
imagecopy($cropped_image, $source_image, 0, 0, $source_x, $source_y, $cropped_width, $cropped_height);
// 画像の縮小
imagecopyresampled($target_image, $cropped_image, 0, 0, 0, 0, $target_width, $target_height, $cropped_width, $cropped_height);

header('Content-Type: image/jpeg’);
imagejpeg($target_image);
imagedestroy($source_image);
imagedestroy($target_image);
imagedestroy($cropped_image);
}

imagecropperを呼び出すサンプル
<?php

//画像サイズ500×400;

$image=’/images/big.jpg’;

//100×80サムネイルにカット

imagecropper($image, 100, 80);

?>