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Create an online art gallery using Satori - Mark Graham looks at a technique to help you scan A3 images on an A4 scanner and then stitch them together using Satori image editing software.
Words Mark Graham. Images reproduced by kind permission of Toby Barclay
My friend, Toby, inherited a number of etchings by the artist Nathaniel Sparks. Nat, cousin to Thomas Hardy OM, was a prolific artist, producing many sketches, watercolours and oils but is best known for his prints and etchings including landscapes, portraits, spirtual images and views of many famous buildings in London and the provinces. He was a prodigiously gifted draughtsman with an acute eye for detail and, toward the end of his life at least, a tendency to the gothic. His later works remind me of Peake's Gormenghast or the Carceri of Pirenesi in their fervid, visionary intensity. By contrast, his earlier works are mostly exquisitely rendered, if idealistic, studies of the English landscapes (and townscapes) of his time. To view his work and learn more about his life please visit www.natsparks.co.uk
Self-Portrait 1926 by Nathaniel Sparks
Toby wanted to create an online gallery where he could display the prints and hopefully sell a few. He also wanted to be able to supply, on CD-ROM, a high-resolution version of the gallery.
Satori (PhotoXL or FilmFX) is ideally suited to this task. I intended to scan the prints and save them in Satori at a resolution high enough to give us the necessary headroom so, when finished and cropped, the bitmaps (on CD-ROM at least) would reveal all the amazing detail contained in these incredible etchings.
There seemed to be one major stumbling block - the prints were all around A3 size and we only had an A4 scanner. They would need to be scanned in sections and stitched toegther using software on the computer. Some were large enough to require four A4 scans.
Taking Tiger Mountain by Strategy
We also decided to work in full colour throughout, despite the fact that 90% of the prints were monochrome. Our experiments in greyscale simply looked flat and dull and, in any event, these old prints were inked in all shades of sepia and, over Nathaniel's working life, he employed many different types and shades of paper stock. None were now pure white; if any had ever been.
Finally we worked out a modus operandi that we would apply to all 150+ images to manage and reduce to a minimum the amount of time the task would take.The order of battle seemed to be: Scan, Save, Photo-Stitch, Save, Color-Correct, Crop, Save.
Having worked out the dpi we'd adopt throughout the process, we began scanning the images, section by section.
The resulting image sections were saved as Satori RIR files and, provided that you have version 2.29 (or above) of Satori PhotoXL or Satori FilmFX you can follow the step-by-step below by first downloading the images sections here (Download images, 1065 Kb). I've chosen a rendering of the North Porch of Westminster Abbey, an early work that shows Nat's mastery of perspective and really glories in the gothicism of the Abbey without the darker, more gloomy overtones of his later work.
Please note: if you have version 3 of Satori you can use the installed PhotoStitch Wizard for this composition however this tutorial touches on important, everyday issues, such as Canvas Resizing, Move Layer and the Alpha Channel, which may be of interest to all users
Simply a Matter of Work
The top half of Westminster Abbey will be displayed.
Next click Open again and select Abbey Bottom.jpg. This time, at the Load to Layer dialog you'll see that the new image is being directed to a New Layer - this is what we want - the top half in one layer and the bottom half in another. However we definitely do not want to stretch or squeeze the new image as we open it - check the radio button next to Keep Resolution in the Current Layer Action panel to prevent this, then click OK.
This will launch the Large File Warning dialog. Click Continue to open the incoming jpg directly without conversion.The incoming image is opened into a new layer that obscures the previous layer/image for the time being.
2 Before we consider repositioning the images with respect to each other, we need to enlarge the dimensions of the current canvas to create the necessary space to move into. Although Satori is resolution-independent, these scans (bitmaps) are not. Therefore to preserve the original resolutions (& avoid scaling) we alter the Canvas dimensions instead. Click the Canvas button on the Actions Palette to switch to Canvas Actions.
Click the Change Size button in the Sizing panel to launch the Resize Canvas dialog. You'll see that it reports the current dimensions in pixels - we want to alter the height of this canvas so type a value of xxx in the Y field to double the height.
Ensure that the Keep To Original Size On New Canvas option is checked and click OK to effect the change.The canvas now displays the image in the top half and emptiness below.
4 Once the two layers are lined up correctly you'll notice you can still see the join and the reasons for this are both subtle and complex. It's to do with the properties of light, lenses and digital imaging and all captured images tend to be brighter at the centre than at the edges. We can compensate for this with a little technical trickery by blurring the edges of the transition between the two.
Currently the top edge of the top layer, i.e. the lower half of the Abbey, simply cuts off abruptly, allowing the image below to be revealed above. But there is an overlap between the images and we can use this to advantage.
Click the Paint button on the Actions Palette to switch to Paint Actions and then click to select the Airbrush from the Brushes tab.
Then from the Geometry Actions palette, Shapes tab select the Lines tool (or click the icon on the Tool Shortcuts toolbar) and click the Cut button to direct the resulting Line object to the Alpha Channel of your layer.
You can control the edge softness of this line by setting the Feather controls in the Geometry Actions, Property tab to 50 pixels for x and y and an Outline Width of 150.
Next click the Restrain Horizontally tool on the Grid Restraints toolbar (see under View menu if you don't have yours currently displayed). This will cause you to achieve a perfectly straight, flat, horizontal line. Now click in, but right at the edge of, the image window as close as you possibly can to the point of overlap and drag to the right before releasing on the opposite side to finish the line.
At this stage save the work - select Save As from the File Menu and save as Abbey.rir. This will launch the Save Bitmap As dialog - accept all the default settings and click OK. The image will be saved for future use.
In next month's Satori tutorial we will show you how to Crop the image, Color-Correct it, and Optimize it for the Web.