Subir imagen con un tamaño fijo

[alvaro_trewhela]

no lo he probado, pero debería andar bien:

Código PHP:

function resize($img,$mW,$mH){
 
// Only do something if is a image file
$fi = new finfo(FILEINFO_MIME); 
$type = explode(";", $fi->file($img))[0];
$im = null;
 
    if($type == "image/jpeg"){
    $im = imagecreatefromjpeg($img);
    }
    else if($type == "image/png"){
    $im = imagecreatefrompng($img);
    }
    else if($type == "image/bmp"){
    $im = imagecreatefrombmp($img);
    }
    else if($type == "image/gif"){
    $im = imagecreatefromgif($img);
    }
    else{
    return null;
    }
 
// End check if is image
 
list($w, $h) = getimagesize($img); //get dimensions
$nW = $mW/$w; //How much we must resize width
$nH = $mH/$h; //How much we must resize height
$res = false; //Auxiliary variable to know if we must resize or not
 
//Get wich side we must resize most
$major = 0; //major var
    if($nW < 1){ //If we need to resize width
    $res = true; //res true
    $major = $nW; // and major resize side = $nW
    }
 
    if($nH < 1){ //If we need to resize height
    $res = true; //res true
        if($nH > $major) $major = $nH; //if new height is less than major, then major = nH
    }
 
    if($res){ //If is neccessary to resize then...
    $th = imagecreatetruecolor($w*$major, $h*$major); //Creating a thumb for the resized image
    imagecopyresized($th, $im, 0, 0, 0, 0, $w*$major, $h*$major, $w, $h); //resizing
    return $th; //return the thumb
    }
 
//Else we return the im resorce
return $im;
}
 

$img es la dirección completa de la imagen
$mW el ancho máximo permitido
$mH el alto máximo permitido

No lo probé pero creo que debería andar bien