Laravel generate image and add content type header

Question

Hi I'm using php's gd library to generate images. I've decided to integrate this into laravel, and I managed to make it work.

My problem is that if laravel sometimes overwrites my content-type header.

This is my controller:

public function imga($algorythm,$w=false,$h=false){
    if (!$w) $w=rand(250,750);
    if (!$h) $h=rand(250,750);
    $im = imagecreatetruecolor($w, $h);

    //Here some fancy function is called
    if (method_exists($this,'img_'.$algorythm)){
        $this->{'img_'.$algorythm}($im,$w,$h);
    }

    header("Content-type: image/png");
    imagepng($im);
    imagedestroy($im);
}

Most of the times if the image is large enough the browser displays it just as expected, but if the image is to small laravel overwrites the content type header with "text/html; charset=UTF-8".

I've read https://laravel.com/docs/5.4/responses but to make it this way I need to have a string.

So I've looked at this: PHP: create image with ImagePng and convert with base64_encode in a single file? but I'm not sure if this is the right way, it looks like a dirty hack to me.

Should I put the imagepng call inside a view and add the headers there, isn't this a bit overkill?

How to use functions that output data instead of returning it in laravel.

score 1 · Accepted Answer

Laravel controller actions are usually expected to give a response of some sort, which defaults to text/html.

Your fix could be as easy as: (好像在 laravel 控制器中不能这么用,好像只能在php这么用)

    header("Content-Type: image/png");
    imagepng($im);
    imagedestroy($im);
    exit;
}

Alternatively you can use a package like intervention (http://image.intervention.io). From which you can generate an image response.

score 1 · Answer 2

One way would be to capture the image output with ob_get_contents and then make a response with that:

public function imga($algorythm,$w=false,$h=false){
    if (!$w) $w=rand(250,750);
    if (!$h) $h=rand(250,750);
    $im = imagecreatetruecolor($w, $h);

    //Here some fancy function is called
    if (method_exists($this,'img_'.$algorythm)){
        $this->{'img_'.$algorythm}($im,$w,$h);
    }


    ob_start();
    $rendered_buffer = imagepng($im);
    $buffer = ob_get_contents();
    imagedestroy($im);
    ob_end_clean();

    $response = Response::make($rendered_buffer);
    $response->header('Content-Type', 'image/png');
    return $response;
}

EDIT: Just saw your link, this is basically just an implementation of that.

If you want a "more laravel" way, you could save the image, return it, then delete it:

public function imga($algorythm,$w=false,$h=false){
    if (!$w) $w=rand(250,750);
    if (!$h) $h=rand(250,750);
    $im = imagecreatetruecolor($w, $h);

    //Here some fancy function is called
    if (method_exists($this,'img_'.$algorythm)){
        $this->{'img_'.$algorythm}($im,$w,$h);
    }

    // store the image
    $filepath = storage_path('tmpimg/' . uniqid() . '.png');
    imagepng($im, $filepath);
    imagedestroy($im);

    $headers = array(
        'Content-Type' => 'image/png'
    );

    // respond with the image then delete it
    return response()->file($filepath, $headers)->deleteFileAfterSend(true);
}

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Laravel generate image and add content type header

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