CCaptcha displaying no image yii - yii

Question

I have a user registration form, in which I am trying to display a Captcha image by using Yii widget CCaptcha, however my image link appears broken,
Controller file:
public function actions()
{
return array(
// captcha action renders the CAPTCHA image displayed on the contact page
'captcha'=>array(
'class'=>'CCaptchaAction',
'backColor'=>0xFFFFFF,
),
);
}
Model File:
public function rules()
{
return array( array('verifyCode','captcha','allowEmpty'=>!CCaptcha::checkRequirements(),'on'=>'insert'),
);
}
And view file:
<?php if(CCaptcha::checkRequirements()): ?>
<div class="row">
<?php echo $form->labelEx($model,'verifyCode'); ?>
<div>
<?php $this->widget('CCaptcha'); ?>
<?php echo $form->textField($model,'verifyCode'); ?>
</div>
<div class="hint">Please enter the letters as shown.
<br/>Letters are not case-sensitive.</div>
<?php echo $form->error($model,'verifyCode'); ?>
</div>
<?php endif; ?>
As a answer provided somewhere I also tried giving the access rules in my controller file as
public function accessRules()
{
return array(
array('allow',
'actions' => array('captcha'),
'users' => array('*'),
),
);
}
But nothing seems to be working.

Answer 1

The problem was with the controller file,it should have been,
public function accessRules()
{
return array(
array('allow',
'actions'=>array('create', 'captcha'),
'users'=>array('*'),
),
}
whereas I had mentioned the action for captcha at the end, which I figured out is not allowed in Yii. All the allow actions for * should be together.

Answer 2

Yii captcha will create a png image. A possible explanation for the broken image link would be a missing GD extension or imagick extension, which can be identified by the presence of the following text in your error.log:
call to undefined function imagecreatetruecolor
For details and fix see "call to undefined function imagecreatetruecolor" error in PHP & pChart