Sunday, August 29, 2010

Marquee Based Selection design tutorial

The most basic way of making a selection in photoshop is to use one of the standard shaped marquees. The standard shapes are: elliptical and rectangular.

There are also two marquees that select either horizontal or vertical rows that are one pixel wide. These are useful for drawing one pixel wide lines and creating 'pixel stretch' effects
In this tutorial we will be selecting the wheel of a car using the marquee tool.

Note that to remove a selection after it is no longer required (or in order to make a new selection) use the 'deselect' option on the 'select' menu [ ctrl - D ] . Also on the 'select' menu you can use the 'inverse' option to select the inverse of the current selection.

Choose the elliptical marquee from the top left of the toolbar. You may have to click and hold the tool to bring up the menu of marquee tools.

Once the elliptical marquee tool is selected draw an oval selection over the wheel. The easiest way to do this is to hold down the [ Alt ] key after you have started drawing (this will enable you to begin drawing from the centre of the wheel rather than from the top left). Another good tip is to hold down the spacebar while you are holding down the left mouse button. This will enable you to draw and move the selection at the same time.

Having selected the wheel of the car you will want to do something with the selected area. To copy or move it to a new layer, simply select 'New' from the 'Layer' menu and choose either 'Layer via copy' [ ctrl - J ] or 'Layer via cut' [ shift - ctrl - J ]. Thus the selected area of the image will be copied/cut onto a new layer.

Once you have made a selection you can create another selection that subtracts from the original.

Once you have selected the wheel you can remove the centre of the wheel from the selection. Just hold down [ Alt ] while selecting the wheel's centre.

You can also add areas to the original selection. Hold down [ shift ] while selecting the top ring of the Audi logo.

When you have finished adding/removing areas from the original selection you can move the defined area to a new layer or simply shift the selection to a new area on the same layer. To move the selection to a location on the same layer just hold down [ ctrl ] while dragging the selected area. To copy the selection to somewhere on the same layer hold down [ alt ] while dragging the selected area. If you do not hold down [ ctrl ] or [ alt ] you will simply move the location of the selection.

Having made a selection it is possible to create another selection that intersects the original by holding down both the [ alt ] and [ shift ] keys at the same time while drawing the second selection.

Start by selecting the wheel with the elliptical marquee tool. Then hold down the [ alt ] and [ shift ] keys together while drawing a rectangular marquee ( you will need to switch to the rectangular marquee tool) that intersects the original selection. Note: intersection is the default behaviour after a selection has been made, thus holding down [ alt ] and [ shift ] together is optional.

Draw the rectangular selection so that it cuts off the top and bottom of the oval.

Final Tips: Selections can be nudged into position rather than dragged. Thus giving you more positioning control. Nudge selections one pixel at a time using the arrow keys. Hold down [ shift ] to move 10 pixels at a time.

If you have trouble remembering the keyboard shortcuts for adding, subtracting and intersecting selections you can use the buttons on the above toolbar.

If you hold down the [ shift ] key AFTER you click and drag using the marquee tools (rectangular or elliptical) then they will form perfect squares and perfect circles no matter how you drag the mouse.

The way to make the rectangular marquee most useful is to use a 'free transform'. Simply draw a rectangular marquee. Then select 'transform selection' from the 'select' menu. Then go to a corner of the selection, hold down the [ ctrl ] key and drag the corner into place.

Free transformation can also be used with elliptical marquee tool to make fine adjustments and thus find a perfect fit between the selection and the image.

Sunday, 19 November 2006

Marquee 1-Pixel Stretch

The single row Marquee tools (row and column) can be used to create pixel stretch effects.

If you find an image such as this one that contains a gradient that you wish to capture and use elsewhere (e.g. as the background to an element on a web page), use the single column marquee tool.

Here I have selected a gradient using the 'column' tool.

Once you have selected the column of pixels the selection can be copied to a new layer via [ ctrl - J ].

Finally the new layer can be expanded to fill the desired area via a 'free transform'. Hit [ ctrl - T ] or go to the 'edit' menu and select 'Free Transform'. Control handles will appear on the layer and thus it can be stretched to the desired size.

More interesting effects can be created with images like this one.

It has a sharp colour transition that produces a very nice effect.



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