PHP pictures generate thumbnail picture code by comparison_PHP tutorial

The image can be enlarged or reduced by comparison. This needs to be implemented using the functions of the gd library in the php tutorial. We will use imagecreatetruecolor() and imagecopyresampled() to operate

function my_image_resize($src_file, $dst_file, $dst_width=32, $dst_height=32) {
If($dst_width <1 || $dst_height <1) {
echo "params width or height error !";
exit();
}
If(!file_exists($src_file)) {
echo $src_file . " is not exists !";
exit();
}

$type=exif_imagetype($src_file);
$support_type=array(imagetype_jpeg, imagetype_png, imagetype_gif);

if(!in_array($type, $support_type,true)) {
echo "this type of image does not support! only support jpg, gif or png";
exit();
}

    switch($type) {
        case imagetype_jpeg :
            $src_img=imagecreatefromjpeg($src_file);
            break;
        case imagetype_png :
            $src_img=imagecreatefrompng($src_file);        
            break;
        case imagetype_gif :
            $src_img=imagecreatefromgif($src_file);
            break;
        default:
            echo "load image error!";
            exit();
    }
    $src_w=imagesx($src_img);
    $src_h=imagesy($src_img);
    $ratio_w=1.0 * $dst_width/$src_w;
    $ratio_h=1.0 * $dst_height/$src_h;
    if ($src_w<=$dst_width && $src_h<=$dst_height) {
        $x = ($dst_width-$src_w)/2;
        $y = ($dst_height-$src_h)/2;
        $new_img=imagecreatetruecolor($dst_width,$dst_height);
        imagecopy($new_img,$src_img,$x,$y,0,0,$dst_width,$dst_height);
        switch($type) {
            case imagetype_jpeg :
                imagejpeg($new_img,$dst_file,100);
                break;
            case imagetype_png :
                imagepng($new_img,$dst_file);
                break;
            case imagetype_gif :
                imagegif($new_img,$dst_file);
                break;
            default:
                break;
        }
    } else {
        $dstwh = $dst_width/$dst_height;
        $srcwh = $src_w/$src_h;
        if ($ratio_w <= $ratio_h) {
            $zoom_w = $dst_width;
            $zoom_h = $zoom_w*($src_h/$src_w);
        } else {
            $zoom_h = $dst_height;
            $zoom_w = $zoom_h*($src_w/$src_h);
        }

        $zoom_img=imagecreatetruecolor($zoom_w, $zoom_h);
        imagecopyresampled($zoom_img,$src_img,0,0,0,0,$zoom_w,$zoom_h,$src_w,$src_h);
        $new_img=imagecreatetruecolor($dst_width,$dst_height);
        $x = ($dst_width-$zoom_w)/2;
        $y = ($dst_height-$zoom_h)/2+1;
        imagecopy($new_img,$zoom_img,$x,$y,0,0,$dst_width,$dst_height);
        switch($type) {
            case imagetype_jpeg :
                imagejpeg($new_img,$dst_file,100);
                break;
            case imagetype_png :
                imagepng($new_img,$dst_file);
                break;
            case imagetype_gif :
                imagegif($new_img,$dst_file);
                break;
            default:
                break;
        }
    }
}

总结，我们要生成比例生成小图就利用$dstwh = $dst_width/$dst_height;
        $srcwh = $src_w/$src_h;进行判断，然后再生成。

http://www.bkjia.com/PHPjc/632989.htmlwww.bkjia.comtruehttp://www.bkjia.com/PHPjc/632989.htmlTechArticle图片按在比较进行放大缩小，这得利用php教程 gd库的函数现实现，我们会利用到imagecreatetruecolor(),imagecopyresampled()来操作 function my_image_resi...