If you want to use captcha code to protect your website from spam messages, there are a few options such as Google ReCaptcha and captcha.com. Both of them can be integrated into ASP.NET Core applications. However, you may still want to generate the captcha code yourself for some reason, such as your website may be used in mainland China.. This post will show you how to generate and use captcha code in the latest version of ASP.NET Core.
The method I use is from Microsoft official code sample here https://code.msdn.microsoft.com/How-to-make-and-use-d0d1752a but with a few modifications so that it can work with .NET Core 2.x as well as some improvements.
The 1.30 version of BezierCode for Mac is available as a free download on our website. This software for Mac OS X is an intellectual property of Bijokmind. The software lies within Design & Photo Tools, more precisely Viewers & Editors. Beziercodetrial1.22.zip is the common file name to indicate this program's installer. 1 مورد برای عبارت مورد نظر پیدا شد. دانلود BezierCode v1.26 MacOSX - نرم افزار طراحی وکتور برای مک بازدید: 2,519. 1)First enter the no. Of points when the program asks 2)Choose whether you prefer to click or to enter through keyboard in the form of matrix all the x & y coordinates 3)Click on various locations in the window or enter through keyboard the coordinates of all points must be within square brackets for example for 4 points whose (1,2),(4,6),(7,8.
How does captcha work
A simple captcha is generating a random code (numbers or alphabets), save the code to the session, and also make an image to show on the webpage. When a user posts the content back to the server, the server compares the user input captcha with the value stored in session to check if the user has entered a correct captcha code. The workflow is explained in the figure below:
This is a sample in the next version of my blog system:
Implement captcha code in ASP.NET Core 2.1
After understand how captcha code works, let's dig into the implementation.
1. Preparation
First, you need to set your project to allow unsafe code for both Debug and Release configuration.
We need to use classes in System.Drawing.Imaging namespace, so we also need to install a NuGet package:
Because captcha relies on Session storage, so we also have to enable Session support in ASP.NET Core in Startup.cs:
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And also here
Note: Session relies on Cookies, so make sure you accept the GDPR cookie policy first, which is added into ASP.NET Core 2.1 default template.
2. Generate Captcha Image
Create a CaptchaResult class to represent the captcha information:
And a Captcha class for generating and validating the captcha
There are a few things to point out.
1. The letters do not contain all numbers and English alphabets, because some characters are difficult to distinguish, for example: Idatabase 3 30 – organize all your information and database.
- Number 0 and English O
- Number 5 and English S
- Number 1 and English I
2. I comment out Bezier code in function DrawDisorderLine() because when the image is very small, it would be very hard to see the characters if there are Bezier lines on it.
Now, in your MVC controller, create an Action for return the captcha image
Now, try to access this Action, you should get a captcha image like this:
3. Use Captcha Image
Add a new property called CaptchaCode to your model that is used for posting content to the server.
Add a new input field for the CaptchaCode and an image which invokes the 'GetCaptchaImage' Action in above section in your view.
In your Action that deal with user post content, add a logic to check captcha code:
4. Additional Enhancements
You can let the user click and load a new captcha image via jQuery.
I finally got around to writing a test program for the advanced quadratic Bezier y-at-x method. In a parametric curve such as a Bezier, the x- and y-coordinates are parameterized as a function of t in [0,1]. There are occasions when an application needs y as a function of x. One common application is when Bezier curves are used to interpolate animation parameters.
It does seem strange using a drawing package like Degrafa for something that is purely computational in nature. There are, however, some drawing applications in which this capability is useful. I once worked on an experimental interface for a designer that was dynamically drawn. The boundary of a certain UI element was a Bezier curve. Depending on which page the user was viewing, a certain number of menu items were dynamically rendered along the boundary. The x-coordinate boundaries were well-known and used to generate y-coordinates to place the dynamic menu items.
The screenshot from the demo shows the previous three-point interpolation used to generate a quad. Bezier. When an interpolation point is moved, a slider becomes active. The slider’s value represents x-coordinates along the interface. As the slider is moved, two markers appear to denote the y-coordinates along the quadratic Bezier corresponding to the input x-coordinate. There are at most two y-coordinates. The t-parameter at each y-coordinate is returned so that this information may be used in applications to choose one y-coordinate over another in the event that only one is required.
Beziercode 1 26th
As always, update your code base from SVN before playing with the demo. Enjoy!
View demo.
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View source. Aiseesoft hd converter 9 2 8 mm.