Using Virtual Image


What is Virtual Image?

Virtual Image is a new system, unique to Photogenics, that offers many of the benefits of having a virtual memory system without the drawbacks usually involved.

Virutal Image allows you to work with images much larger than you would normally be able to load into Photogenics, indeed you can easily work with an 18Mb image file, even on a 4Mb A1200. You do not need a Memory Managment Unit (MMU), an expensive accelerator card or lots of ram. All you need is your standard Amiga and some free space on your hard drive.

When you have a Virtual Image loaded into Photogenics only a few hundred kilobytes of memory are used (mainly to display the preview image), so you have plenty of memory left to use with your other programs or to edit other images.

Virtual Image works by converting the file you are loading into a temporary file stored on your hard disk. Of course this means that you will need enough space on your hard drive to store this 18Mb file, typically you will want at least twice as much free space on your hard disk than the size of the image you are trying to load.

When you installed Photogenics, you were asked to choose a path for your temporary data. This is assigned to "PgsTemp:" in your s:user-startup file. If you need to permanently change the path for Photogenics's temporary data, edit your s:user-startup file to change the assign. To change temporarily, you can use the Arexx macro ChangePgsTemp.rx, which you can find in the scripts directory.

So.. Let's go through a quick example to show you how Virtual Image works. (This assumes you've got a few megabytes of free space on the hard drive that PgsTemp: points too.. Now would be a good time to check!)

Select 'Open Virtual Image' from the menu, and open the file 'VanishPoint.JPG' from the Graphics/Virtual directory (assuming you've installed the tutorial graphics). This image is 1280x1024 pixels, and normally takes 5 megabytes of RAM to load into Photogenics.

You will notice it takes a little longer to load than normal, that's because it's writing data to your hard disk while it loads.

When it's loaded, you should have a window on your screen with the image shown. Note that you can't resize the window, but you can click on the resize button in the titlebar to hide the image and leave the title bar.

Virtual Image doesn't give you all of this for nothing - there is a drawback. Most of the standard drawing tools (such as spraycan, lines, circles, etc. cannot be used on a virtual image directly (although there is a way around that we'll see in a minute).

So - what can you do with them?

You can save them as another file format (so converting large JPEGs into a different format, eg. ILBM, no longer requires you to have serious amounts of memory).

You can apply the effects (from the Effects list) to the image. All of the effects will work, although some (Perspective, Wave, Linestrokes, etc.) may take a *very very* long time on virtual images!

But you don't have to apply the effect to the full image, you can select a region of the image. In each corner of the virtual image window you'll find a point you can drag with the mouse. Move into one corner, hold down the left mouse button and drag towards the center of the image. By moving the box corners, or by moving the entire box (from the center point), you can select a region. Most, but not all, effects can be applied to the region within the box.

There are some times that effects aren't enough, and you need the full power of Photogenics's paintmodes and airbrush system to adjust an image.

Virtual Image offers a simple and elegant way to deal with this. By selecting a region on scren by moving the box to surround the area you wish to edit, you can click on the scissors icon in the toolbar and the area selected is 'clipped' out into a new buffer. The whole of that area is loaded into memory (so you'll have to make sure you have enough conventional RAM in your computer to deal with the area you selected) and you can edit it as you can with any image you load into Photogenics as a normal image - using the airbrush, cloner, paintmodes, warper and all the other tools.

When you've fixed your changes to this area, simply choose Save into Virtual Image from the menu (or press Right-Amiga S) and the updated area will be written back into the virtual image to exactly the same place it came from (unless you have scaled, rotated or in any other way changed the size of the clipped region, in which case it can't return it to the virtual buffer.

This is ideal, as most of the time you will be wanting to work on small areas of a large image at a time, for example if you have a photograph of someone's face and you want to work in high precision adjusting the colour of their eyes - simply cut out each eye in turn, edit it with the normal photogenics tools, and save it back into the image. It's so easy and so fast. Try waiting for other image processing programs to catch up. They're still loading the original image while you've loaded your image, edited it and saved it out again.

Another advantage of working with virtual images is your data is stored on the hard disk, so if you have a powercut or your computer crashes, you can usually reload the data back in and carry on working with it. Virtual Image temporary files are stored in standard IFF-DEEP format, so you should move the file out of the PgsTemp: directory once you have rebooted (it will have a filename like 12345678.deep), rename it if you want, and load it back in as another virtual image.

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