codeigniter resize image by width - codeigniter

Question

I want to create a new photo using dynamic width only so that the Height then changes depending on the width automatically.
The following code is not working with me.
$w = $width;
$w = $w / 4 ;
$mconfig['width'] = $w;
$mconfig['maintain_ratio'] = TRUE;
$mconfig['source_image'] = 'uploads/watermark.png';
$mconfig['new_image'] = 'uploads/images/watermark/watermark.png';
$this->image_lib->initialize($mconfig);
$this->image_lib->resize();
$this->image_lib->clear();

Answer 1

Try to set the Height also
for example
$config['height'] = 50;

Answer 2

Try this:
//Imagine you need Width 1000px
$height = ($fdata["image_height"] * 1000) / $fdata['image_width'];
$resize_height = (int)$height;
$mconfig['width'] = 1000;
$mconfig['height'] = $resize_height;
$mconfig['maintain_ratio'] = TRUE;
$mconfig['source_image'] = 'uploads/watermark.png';
$mconfig['new_image'] = 'uploads/images/watermark/watermark.png';
$this->image_lib->initialize($mconfig);
$this->image_lib->resize();
$this->image_lib->clear();
Here $fdata["image_height"] is uploaded image height and $fdata['image_width'] is uploaded image width.

Answer 3

Try this,
$uploaded_data = $this->upload->data();
$w = $width / 4;
$config['width'] = $w;
$config['height'] = round($uploaded_data['image_height']/($uploaded_data['image_width']/$w), 2);
$config['image_library'] = 'gd2';
$config['source_image'] = 'uploads/watermark.png';
$config['new_image'] = 'uploads/images/watermark/watermark.png';
$config['quality'] = "100%";
$config['maintain_ratio'] = true;
$this->load->library('image_lib', $config);
$this->image_lib->initialize($config);
if ($this->image_lib->resize()){
$this->image_lib->clear();
return true;
}else{
return $this->image_lib->display_errors();
}