How to display an image without an extension through the direct link in the browser?

Using only .htaccess is not possible, this is because there are several types of image and it would be complicated to add mime-type to each one, however you can redirect to a php handle, for example:

Create a .htaccess: file with this content in the image folder:

RewriteEngine On
RewriteRule ^ proxy_image.php?path=$0 [L]

In the same folder, create a file named proxy_image.php with the following content:

<?php

function mimeType($file)
{
    $mimetype = false;

    if (class_exists('finfo')) {//PHP5.4+
        $finfo     = finfo_open(FILEINFO_MIME_TYPE);
        $mimetype  = finfo_file($finfo, $file);
        finfo_close($finfo);
    } else if (function_exists('mime_content_type')) {//php5.3 ou inferiror
        $mimetype = mime_content_type($file);
    }

    return $mimetype;
}

if (empty($_GET['path'])) {
    echo 'Caminho invalido';
    exit;
}

$path = $_GET['path'];

$extensoes = array('jpeg', 'jpg', 'gif', 'png', 'ico', 'svg');

$fullPath = null;

//Busca pela primeiro arquivo que contiver a extensão (pode implementar glob também, é opicional)
foreach ($extensoes as $extensao) {
    if (is_file($path . '.' . $extensao)) {
        $fullPath = $path . '.' . $extensao;
        break;
    }
}

if ($fullPath) {
    //pega o mime-type do arquivo
    $mime = mimeType($fullPath);

    //Verifica se o mime-type é do tipo imagem
    if (strpos($mime, 'image/') === 0) {
        header('Content-Type: ' . $mime);

        readfile($path);
        exit;
    }
}

echo 'Isto não é uma imagem';
exit;

Then just navigate to something like http://localhost/images/foobar , if there is an image with this

Note that it is possible to implement caching and use Etag along with this code above, as I used in this example of the question (not the answer):

• You can use if-modified-since with "304 not modified" without PHP

  

This response is due to the fact that it has the [PHP] tag in the question.

With PHP:

You can enter Header in PHP:

header('Content-type: image/png');

The type of the document will vary, so you should set image/png only for images are of the same format, you can usually identify the format through its extension, such as .png .

So I could do something like:

$tipo = [
'gif' => 'image/gif',
'png' => 'image/png',
'jpeg' => 'image/jpeg',
'jpg' => 'image/jpeg'
];

$nome = 'image.png';
$extensao = strtolower(substr(strrchr($nome,"."),1));

if( isset( $tipo[$extensao] )) {
   header('Content-type: '.$tipo[$file_extension]);
}

//... { Exibe um "echo" da imagem }

With Apache

You can use .htaccess (or change in httpd.conf if off) to force all files to have a same content-type .

<Location /imagem>
  ForceType image/jpeg
</Location>

This will cause all requests to /imagem to exit with the previously set Content-type . ;)

More information about ForceType can be viewed here.