Photoshop Fusion Tutorial

Photoshop Collage and Fusion Tutorial for Plaque Simulator

Tutorial objective

This tutorial illustrates the use of Photoshop CS5 (newer versions of Photoshop will be similar) to create a rescaled fundus photo collage for export to Plaque Simulator with optional fusion of fluorescein angiography.

The final result is illustrated on the right. The 3 source images are illustrated below.

The sample source images may be found in the tutorial images section of the PS6 full download for version 6.1.9 or later (e.g. Plaque Simulator Folder/Plaque Simulator Data/(Tutorial Images)/PS6/Photoshop Tutorial/).

In this tutorial we will:

Rescale excessively large, high resolution source image files down to a size that is manageable by PS6 and any subsequent .pdf documents.
Crop and fuse the rescaled images into a collage of Photoshop layers.
Flatten the layered collage for export to PS6 as a .jpg file.
Export the file.

Fluorescein angiography is a technique for examining the circulation of the retina and choroid using a fluorescent dye and a specialized camera. In the fluorescein angiography image a choroidal melanoma typically shows a mottled hyperflourescence and diffuse late staining of the mass and its overlying subretinal fluid.

Fusing a fluorescein angiography image with the retinal collage can at times help to locate the fovea and to differentiate tumor from other forms of retinal damage that give an abnormal appearance to portions of the retina.

Photo1.jpg

Photo2.jpg

FluoresceinAngiography.jpg

Rescale Photo1.jpg

The pixel dimensions of images imported into PS6 (e.g. CT MPRs, ultrasound, fundus collages) should not exceed roughly 800 x 800 pixels. PS6 also expects all images to be initially calibrated at 72 dpi, ie each pixel being an OSX printer point of 1/72nd inch. PS6 can import and handle images that do not meet these specifications but interactive responsiveness will degrade, and PS6 patient file and .pdf document size could become very large.

In Photoshop:

Open the file Photo1.jpg.
Select Image Size... from the Image menu.

In the Image Size window, observe that the original image dimensions of 2392x2048 pixels are much larger than required by Plaque Simulator. We should rescale the image to roughly 800 pixels wide at a resolution of 72 dpi. Begin by enabling the constrain proportions checkbox and setting the resample image menu at the bottom of the window to bicubic sharper.

Next, change the pixel dimensions and document size popup menus from pixels to percent. The width and height fields will change to read 100%. Then change the document size resolution from 100 to 72 pixels/inch.

Lastly change the pixel dimensions width from 100% to 33.33% (800 pixels is roughly 1/3 of the original width). Changing any text field will synchronize all the other fields when constrain proportions is enabled. Click the OK button to close the Image Size window.

Photo1.jpg just after opening in Photoshop CS5 is 2392 x 2048 pixels at 100 dpi. This is too large for efficient use in Plaque Simulator.

Photo1.jpg rescaled by 1/3 to 797 x 683 pixels at 72 dpi for best performance with Plaque Simulator.

Rescale Photo2.jpg

Repeat the process for Photo2.

Photo2.jpg just after opening in Photoshop CS5 is 2392 x 2048 pixels at 100 dpi. This is too large for efficient use in Plaque Simulator.

Photo2.jpg rescaled by 1/3 to 797 x 683 pixels at 72 dpi for best performance with Plaque Simulator.

Rescale FluoresceinAngiography.jpg

The file FluoresceinAngiography.jpg is already a good size for Plaque Simulator at 768x768 pixels. All we need to do is change the original dpi from 96 to 72. In the Image Size window, change the pixel dimensions and document size popup menus from pixels to percent. The width and height fields will change to read 100%.

Then change the document size resolution from 100 to 72 pixels/inch. Click the OK button to close the Image Size window.

Make a fundus collage of the retina using the two fundus photos

To make a collage of the retina using the two photos we will convert the photos into Photoshop layers. By making one of the layers translucent we will use the optic disc and blood vessels as landmarks to assemble the collage.

Select the elliptical selection marquee tool.
In the toolbar set the marquee style property menu to fixed size.

Use the selection marquee to outline the portion of Photo2.jpg that will become a Photoshop layer. It may take a few repetitions to determine the correct dimensions. You can initially estimate the dimensions from the rulers at the top and side of the Photo2.jpg window.
- Estimate the width and height as 745 x 745 pixels. Enter these values in the toolbar width and height fields in px.
- Click the cursor in the Photo2.jpg window to create the selection marquee.
- Drag the marquee to outline the portion that will become a layer.
From the Edit menu select Copy or press command-C on the keyboard.
From the File menu select New or press command-N on the keyboard.
In the New dialog set the file name to fundus which satisfies the Plaque Simulator image naming convention for a fundus collage. The new window dimensions will default to the size of the region that was copied. Change the dimensions to something larger than the estimated size of the finished collage. In this case the new image will be 900 x 900 pixels, 72 dpi, 8 bit RGB Color with a transparent background. Click the OK button to exit the dialog and create the new blank image.
From the Edit menu select Paste or press command-V on the keyboard to add the copied region of Photo2.jpg to the new blank fundus window as layer 1.
Select the arrow cursor and drag layer 1 away from the center of the new fundus collage.
.

Select the same kind of circular region from Photo1.jpg and paste it into the new fundus collage window as layer 2.

In the layers list set the layer 2 opacity to 50%.

In the layer toolbar enable show transform controls.
Rotate, translate, and rescale layer 2 so that the blood vessel landmarks overlay layer 1 as closely as possible.
To translate layer 2 click the arrow cursor within the transform outline of the layer and drag.
To rotate layer 2 click the arrow cursor near a corner of the transform outline and drag.
To rescale layer 2 click the arrow cursor in one of the transform corner control boxes and drag while holding down the shift key to keep the original aspect ratio.
To finalize the transform click the check mark in the toolbar.

In the layers list reset layer 2 opacity to 100%.
Then select layer 1 and move it above layer 2 by dragging its position in the list of layers.
Layer 1 will now be outlined by the layer transform controls and will be positioned in front of layer 2 completing the assembly of this simple 2 layer fundus collage.
Collages covering a larger portion of the retinal surface may require many layers and may require less overlap of the layers.

OPTIONAL: Fuse a fluorescein angiography image with the collage

To fuse the fluorescein angiography (FA) image with the fundus collage we will add the FA image as a translucent Photoshop layer and then rotate and rescale the FA layer to match the fundus collage using the disc and blood vessels as landmarks.

In the FluoresceinAngiography.jpg window of Photoshop:

Select the rectangular marquee tool.
In the marquee toolbar select normal from the style popup menu.

Click the marquee cursor in the upper left corner of the image and then drag until the entire fluorescein angiography (FA) image has been selected.
From the Edit menu select Copy or use the keyboard combination command-C.

In the recently created collage window (now titled fundus.jpg) of Photoshop:

From the Edit menu select Paste or use the keyboard combination command-V.
This will add the previously copied FA image as a third layer to the collage.

Change the opacity of layer 3 to 50%.

Transform the FA layer by rotating and rescaling using the blood vessels and disc as landmarks.
To finalize the transform click the check mark in the toolbar.

Export the collage to Plaque Simulator

To prepare the collage for export to plaque simulator we will next flatten the image from 3 layers down to a single layer, fill the extra space surrounding the collage with black, crop the image to fit the useful part of collage, and lastly save the collage as a .jpg file.

In the Photoshop tool palette:

Set the background color to black. This is done using the color controls near the bottom of the palette.
Select the paint bucket fill tool.
In the paint bucket toolbar set mode to normal, opacity to 100%, tolerance to 0, and enable the antialias and contiguous check boxes.
Click the paint bucket tool cursor in the white region surrounding the collage.

The white region surrounding the collage will fill with black. We fill the background of fundus collages with black for export to Plaque Simulator because in Plaque Simulator anything black in a fundus collage will become transparent.
Select the rectangular marquee tool.
Using the marquee tool, click and drag to outline the bounding box of the collage.
From the Image menu select Crop.
The image will crop to the bounding box.

From the File menu select Save As...

In the Save As sheet:
- Navigate to where you would like to save the file.
- Set the Format popup menu to JPEG.
- You can optionally disable the embedded color profile to reduce the file size a bit.
- Click the Save button to save the file.

If you are presented with a JPEG options dialog while saving the file:
- Set the Image Options quality to 12 or maximum.
- Set the Format Options quality to baseline standard.
- Click the OK button to save the file.