All you should need is a single Image size step where resample is not check and you pull down and select Percent as the change units. The you enter the percent you wand in the width or height. the top section should be grayed out because you not interpolating the image so no pixels will change. Other Options like constrain and interpolation are also not available. All that will change is the image DPI print resolution setting. The Image will still be the same image have the same pixels and aspect ratio all the changes is the print size.
You wrote "I just want to enlarge to correct a mis-scaling." If by miss-scaling you mean the current image is not the correct size and has a different aspect ratio then the image you want you need two steps. The percentage change to bring it to with the print size you want then a Canvas size step to add the missing pixels so the image has the correct aspect ratio with canvas addec to two if its sides
I see what you mean. The action does not seem to record that you have resampling turned off, and just assumes that you want the image at 100%. Only way I know to get around this is with a script. The below script will resize an image to 10 inches in width, but not resample the image. You have to use pixels as units. So the first undefined is the width, and the second is the height. By entering "undefined" it tells PS to adjust those values to whatever value you did enter. In this case, in the resolution slot, I out the image width divided by 10, which will put the width at 10". You could make a script that test for vertical or horizontal and use whatever size you want.
var doc = activeDocument
app.preferences.rulerUnits = Units.PIXELS
Wow, thanks csuebele, I am not familiar with scripts and have so far only used a few in InDesign, but would like to learn more.
I see there's a scripting guide pdf in the PShop application folder.
Would I use AppleScript for this?