Photoshop + MATLAB
14 March 2009
As a researcher who works with digital images, I have two programs open all day long: Photoshop and MATLAB. Since Photoshop CS3 came out about two years ago, I have been increasingly using both programs together. I frequently send images to Photoshop from MATLAB and also read images back into MATLAB from Photoshop. In this post, I give a demonstration of some of my favorite ways to use these programs together.
Not surprisingly, Photoshop has a great set of tools for navigating around images. Once you know the keyboard shortcuts, you can quickly zoom-in to a specific region or zoom out to see the entire image. You can also move around at a set zoom level by dragging the red box in the Navigator pane. You can certainly show images and zoom within MATLAB, but I find Photoshop’s tools to be more comfortable to use. I also like to toggle between the color channels and check the histogram.
For many image processing algorithms, the output can be viewed as an image. For example, in a segmentation task, the labels can be converted to grayscale values. In such cases, it is useful to overlay the result and original image to visually compare the two images at every pixel. Photoshop’s layers are a natural way to create overlays.
The two commands for opening a set of images in layers are psnewdocmatrix and psnewlayermatrix. I find it useful to toggle layer visibility and to change the opacity of the layers.
In recent projects, I have also been sending all intermediary results to separate layers and saving the psd file as a record of the full algorithm. As the code changes, I can judge improvements by loading the psd files of past results.
In this clip, I show how to make a quick mask. The image can be any image in
your MATLAB workspace, though if it is double-precision, you may want to convert
it to an 8-bit image with
im2uint8 before sending it to Photoshop.
The basic steps are:
psnewdocmatrix: Create a new Photoshop document from an image in the MATLAB workspace.
- New Layer: Make a new layer for the mask
- Edit->Fill: Fill the layer with black
- Quick Selection Tool: Select the object with a few strokes
- Edit->Fill: Fill the selection with white
psgetpixels: Read the pixels of the visible layer back into MATLAB