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2009 31 Dec

Mastering The Magic Wand In Adobe Photoshop CS4

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Adobe Photoshop CS4 is a difficult program to master without some expert assistance. When I run courses on Photoshop, tools like the magic wand and the clone tools are usually the ones which everyone finds the easiest to start using because they give such immediate results. The Magic Wand is one of three tools in Photoshop which are dedicated to making selections. The Magic Wand works by selecting colours within the image adjacent and similar to any pixel that you click on. Pixels of dissimilar colour act as barriers to selection and so the selection ripples outwards from the point you click on.

Typically, when using the magic wand, you will select part of the area that you want with your first click and you will then need to add and subtract from the selection, perhaps switching to the other selection tools from time to time. Photoshop offers you two ways of modifying a selection: you can either use modifier keys on you keyboard or activate the modifier icons on the options panel normally displayed below your menu bar.

To add more pixels to your selection, hold down the Shift key while clicking with the Magic Wand on a part of the image which is not yet selected. To subtract from the selection, hold down the Alt key and click on the part of the selection which you wish to deselect. The selection modifier icons are situated on the left of the options panel. There are four of them: new selection, add to selection, subtract from selection and select intersection. These icons effectively allow you to change selection mode on a permanent basis. Thus, for example, you could click on the second of the four icons when using the Magic Wand and click continually on different parts of a subject until it was completely selected.

A simple trick for selecting a subject against a uniform background such as a wall or the sky is to use the magic wand to select the background and then invert the selection by choosing Select – Inverse. A slight variation on this technique is to make a rough selection which completely encloses the subject as well some of the background and then to use the Magic Wand in subtract mode to remove the background from the selection.

The number of pixels which the Magic Wand selects when you click on part of the image can be controlled by changing a setting called tolerance. Tolerance determines how far a pixel can vary from the pixel that you click on and still be included in the selection. The default tolerance is 32 and the maximum is 255.

Are you looking for training on Adobe Photoshop? We offer Adobe Photoshop CS4 training in London and all over the UK.

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2009 15 Dec

Using The Different Types Of Validation Server Controls In ASP.NET

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The ASP.NET environment provides developers with many tools for speeding up the development process. Developers often spend a lot of time writing code which checks the data entered by the user in a web form. ASP.NET validation server controls cut down development time by removing the need to write complex validation code to handle client-side and server-side validation of information entered into a form by a user. The controls do more than just validation; they also perform browser detection to check whether JavaScript is enabled on the client’s browser. If JavaScript is enabled, the control sends the necessary JavaScript code to the client; if JavaScript is not enabled, server-side validation takes place.

ASP.NET offers developers six validation controls available in ASP.NET: the RequiredFieldValidator, the CompareValidator, the RangeValidator, The RegularExpressionValidator, The CustomValidator and the ValidationSummary.

The most frequently used and the most basic is the RequiredFieldValidator. It simply prevents the user from submitting the form without first entering or choosing a value in a required form field. It is often used in conjunction with other validators since, naturally, multiple validators may be applied to the same field.

Next, we have the CompareValidator which performs comparison on the contents of a given form field and another element. The type of comparison can be varied to reflect the type of data the field contains. Thus, for example, if the data is numeric, operators such as equal to, greater than and less than can be used. The comparision will often involve two fields. For example, if your form requests the user’s email address twice to ensure that it has been entered correctly, the CompareValidator can be used to check that the two email address fields contain the same entry.

The RangeValidator performs a special type of comparison; it verifies that the value entered by the user falls within a certain range. It can be used to perform checks within text ranges, number ranges and date ranges.

The RegularExpressionValidator allows you to define a regular expression against which the value entered in a field can be validated. Regular expressions are a widely-used standard for checking that a given string conforms to a certain pattern. They are notoriously arcane but Visual Studio and Visual Web Developer Express make the process easy by providing a Regular Expression Editor which contains regular expressions for matching common types of data such as email address, web URLs as well as postcodes and telephone numbers for several different countries.

The CustomValidator control offers maximum flexibility in performing validation checks, allowing developers to write custom validation code. The code may be client-side or server side.

The final validation server control, the ValidationSummary control is not itself used for validation. Instead, it works in conjunction with the other controls to provide a mechanism for consolidating error messages generated by other validation controls. It is particularly useful for large forms.

Need to master web development using ASP.NET? We offer Microsoft ASP.NET training courses in London and all over the UK.

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