MGIF 5.01

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It's strange, isn't it, that there's so many image processors around these days? At one time the choice was simple. There was the Atari Image Manager (AIM) - a programme that only a few devotees ever got to grips with - and that was it. Image processing was a black art confined to Universities, the military and NASA.

The legacy of this was that most image processors were so technically biased that most users never got beyond the play slopes. You knew they were capable of marvellous effects - their example pix were invariably stunning - but your own attempts always seemed to end up as a white smudge on a black ground.

And that's why I'm so impressed with MGIF v5.01. It's a technical programme, written by a technically-minded programmer, but it comes with enough explanation, examples and documentation that even a neophyte can produce equally stunning results within the shortest possible time.

And it's also free; a major selling point. So I loaded it onto my hard drive and took it for a spin on a 4Mb STE with a high res monitor.

But what does it do?

MGIF is an image processor and picture displayer that runs in any Atari resolution up to and including True Colour on the Falcon. It preserves the colour depth of the original image regardless of the current display resolution, and it allows you to work on either single colour channels (Red, Green or Blue) or all the RGB channels combined.

To translate that into plain English, it means that you can alter, display, convert and save pictures with a far larger number of colours than can ever be shown on the screen. A dithered representation is displayed, but the image itself remains unchanged in memory and can be worked on and saved without any form of dithering or colour reduction being imposed on it.

MGIF can be run as a TOS, GEM or GTP programme. Most users will probably want to run it as a GEM programme (the TOS version is for use with MinT), but it can also be set up to act as a slideshow or installed from the Desktop to work as a picture viewer. It runs on any ST, STe or Falcon (using the DSP chip to full advantage) and can load JPG, JPE, GIF '87 & '89, TGA, PPM, PI1/2, AIM, and (X)IMG pictures, along with its own .FL (Flicker) format. The results can be saved in GIF '87, TGA, PPM, or .FL formats, as well as monochrome IMG files for use in WP and DTP progs. I was surprised that MGIF couldn't load or save in Tiff format - the image processing standard - but that's a minor problem that can be easily overcome with a decent picture converter.

The 'IMG save' option is particularly well handled, as it gives you the choice of saving the image with either with Floyd-Steinberg dithering (for use on screen) or with an ordered dithering that's more suitable for printing. Another welcome refinement is the option to save the output at any given size (in pixels, cm or inches), and at any DPI (Dots Per Inch) setting to match your printer. This means that the dimensions shown on screen are the ones that the image will occupy when printed on the page.

**And how does it do it? **

MGIF's image processing options operate on two different levels: alterations to each pixel, or alterations to a 3 x 3 grid of pixels. Anyone used to other image processing programmes will be surprised at how little time these operations take.

The individual pixel options include: Histogram Equalise, Invert, Log Scale, Threshold Setting, Contrast Expansion, Brighten and Darken. These are relatively straightforward operations that affect the tonal balance, contrast or intensity of a picture.

The area operations are: 3x3 Convolutions (Low Pass 1-3, High Pass 1-3, Laplace 1-3, Shift Diff, Smooth, Grad. Dir., Kirsch, Sobel and Line), plus Blur, Local maximum (erosion), Local minimum (dilation), Median, Oil and Pixelise. These operations, or 'filters', can be altered in many ways and are used to extract the edges of an image, sharpen it, produce an embossed image, blur it (soft focus), remove 'noise', disguise previous dithering, or even to produce a pixelated 'Crimewatch' effect on a familiar face.

My own favourite is the Oil Paint filter that averages small areas of any picture and then represents them as oval brushstrokes. Running a picture through the filter several times results in an almost Impressionist style that can turn a face or a nude (for example) into a work of art.

Before
After

Pictures can also be re-sized, mirrored, trimmed and rotated, and can even be given a coloured border with a user-defined width.

First impressions

I found MGIF rather confusing at first, but its comprehensive on-line help meant that I was soon using it with a confidence that I hadn't felt with other programmes of its type. (The on-line help comes in the ST Guide hypertext format, so you'll need a copy of ST Guide to get the most from MGIF.)

The help file includes simple definitions of the key image processing concepts, such as: histograms; greyscale, mapped and 24-bit colour; ordered dithering; Floyd-Steinberg dithering; halftones and convolutions. It also includes brief but informative tutorials that explain in plain English the effects and uses of all the various filters, and the programme comes with a series of pictures that show the effect of each filter on a small example picture. The quality of the documentation, for once, matched the professionalism of the programme itself.

And in practice...

On loading, an 'Initialisation Box' appears that allows you to allocate the amount of memory the programme will use, and whether MGIF should run in 'Flicker', normal, or a 24-bit mode that uses one buffer per colour channel. You can also opt for single buffers and screens if you're running the programme on a smaller memory machine.

The 'Flicker' option is for mono monitor users and shows MGIF's origins as a pseudo-greyscale Gif viewer. The image is loaded, converted to greyscale, and then drawn rapidly on the screen with an ordered dither, followed by a Floyd-Steinberg dither. The two images are then displayed alternately at high speed to give an impression of a greyscale picture on a mono monitor. It sounds crude, but it looks superb! (The Flicker mode can also be used for colour pictures, but I wasn't able to test that as I only had a mono monitor to hand.)

MGIF uses the idea of Source and Destination buffers: a 'before' and 'after' approach that makes it almost impossible to over-write the original image. It took me a while to get used to this, but once I had I found this method surprisingly easy to use. The 'Source' buffer remains unaltered during any operation, and the result is then viewed from the 'Destination' buffer. The Source and Destination buffers can be interchanged if necessary, and this means that you can carry out repeated operations by copying the results to the Source buffer and repeating the operation once more.

To show what MGIF is capable of, here's a few pictures that show the different stages I went through while creating a logo for the Kelstar Atari User Group. I already had a IMG file that I'd 'made earlier' with Textstyle and Megapaint, so I loaded it into MGIF and waited a few seconds while it converted it from bitmap to greyscale, all ready to be manipulated.

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The image was then embossed by using a Kirsch filter set from the NW direction with a bias of 130. This is how it appeared in the Destination buffer, before being moved back to the Source buffer for the next operation:

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So far, so good, but the next stage gave it that extra-added magic that I'd been looking for. I used MGIF's 'Linear shade' option to create a greyscale fade, altered a couple of settings and then added it to the embossed image with the 'Combine' function. Voila - one shiny metal logo ready to be saved out as either a greyscale Gif or a half-tone IMG file all ready for printing. (And all with the very minimum of skill and effort on my part...)

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Conclusions

The only drawbacks I've found with MGIF are that (i) you can't load or save TIFF images, and (ii) that you can't save your current configuration: the settings can only be made permanent by exiting the prog and editing the Options file by hand.

MGIF is a professional and well thought out programme, and one that's easier to use than most other image processors. It's fast and reliable, but its documentation needs to be read thoroughly if you're to get the best from the programme. In short, MGIF takes a while to learn, but its possibilities more than justify the effort.

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Product
MGIF 5.01

Minimum System
All Atari's, 512K memory


John Weller



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