php圖片壓縮不失真的實(shí)現(xiàn)方法：首先設(shè)置圖片壓縮比；然后通過(guò)“getimagesize”函數(shù)獲取原圖尺寸；最后使用“imagecopyresampled”函數(shù)壓縮圖片即可。
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php解決圖片無(wú)損壓縮
代碼如下：
header("content-type: image/jpeg");$file = "111.jpg";$percent = 1.5; //圖片壓縮比list($width, $height) = getimagesize($file); //獲取原圖尺寸//縮放尺寸$newwidth = $width * $percent;$newheight = $height * $percent;$src_im = imagecreatefromjpeg($file);$dst_im = imagecreatetruecolor($newwidth, $newheight);imagecopyresized($dst_im, $src_im, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);imagejpeg($dst_im); //輸出壓縮后的圖片imagedestroy($dst_im);imagedestroy($src_im);我發(fā)現(xiàn)用php的imagecopyresized把大圖片縮成小圖片時(shí)，圖片會(huì)變得很模糊，這時(shí)候要提升清晰度不如用 imagecopyresampled 代替 imagecopyresized也許會(huì)更好。
注：壓縮有損失是必然的，看的清楚與否實(shí)際上就是是否接受這個(gè)范圍的問(wèn)題.比如你圖像上原圖有些點(diǎn)是2px,但是你壓縮5倍，那么這些點(diǎn)就會(huì)消失。
<?php / * desription 壓縮圖片 * @param sting $imgsrc 圖片路徑 * @param string $imgdst 壓縮后保存路徑 */function image_png_size_add($imgsrc,$imgdst){ list($width,$height,$type)=getimagesize($imgsrc); $new_width = ($width>600?600:$width)*0.9; $new_height =($height>600?600:$height)*0.9; switch($type){ case 1: $giftype=check_gifcartoon($imgsrc); if($giftype){ header('content-type:image/gif'); $image_wp=imagecreatetruecolor($new_width, $new_height); $image = imagecreatefromgif($imgsrc); imagecopyresampled($image_wp, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height); imagejpeg($image_wp, $imgdst,75); imagedestroy($image_wp); } break; case 2: header('content-type:image/jpeg'); $image_wp=imagecreatetruecolor($new_width, $new_height); $image = imagecreatefromjpeg($imgsrc); imagecopyresampled($image_wp, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height); imagejpeg($image_wp, $imgdst,75); imagedestroy($image_wp); break; case 3: header('content-type:image/png'); $image_wp=imagecreatetruecolor($new_width, $new_height); $image = imagecreatefrompng($imgsrc); imagecopyresampled($image_wp, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height); imagejpeg($image_wp, $imgdst,75); imagedestroy($image_wp); break; } } / * desription 判斷是否gif動(dòng)畫 * @param sting $image_file圖片路徑 * @return boolean t 是 f 否 */function check_gifcartoon($image_file){ $fp = fopen($image_file,'rb'); $image_head = fread($fp,1024); fclose($fp); return preg_match("/".chr(0x21).chr(0xff).chr(0x0b).'netscape2.0'."/",$image_head)?false:true; } ?>