Background: I am using Illustrator to combine several raster images. I apply scaling and clipping masks to them. Next, I try - if possible - to avoid non-integer resampling steps during subsequent printing. I.e. if an image originally was e.g. 150 ppi and the publisher asks for 150 dpi, I aim for 150 (original dimensions) or 300 ppi (i.e. the size was downscaled by an integer factor of 2), since
- (a) most times I am very close to such integer factors anyway, or
- (b) picture dimensions need to be reduced to meet minuimum ppi/dpi without "upsampling".
Question: Is there a way to tell AI to scale image dimensions to meet a defined ppi (at least necessary in scenario b)?
E.g., an image which is 140 ppi should get slightly smaller to become 150 ppi (I am NOT looking for upsampling!). I know I can see the resolution via Document Info window / flyout embedded (or linked) images and manually calculate a scale factor (actual ppi / desired ppi), but I am looking for a solution that is automatic and has no rounding issues.
Question (optional part): Am I wrong to aim to avoid non-integer factors b/o quality issues in subsequent resampling steps where possible (scenario a)?
Edit for clarification: I am dealing with composite figures, where I need to fine-adjust the size (millimeters) of each individual subfigure (bitmaps, may be photographs, microscope images, MRI scans, ...). Subfigures are prepared at sufficient resolution that allow using them at integer multiples/fractions of original mm dimensions to meet publisher-desired ppi and to fit to the other subfigures. Once the subfigures are at an approximately useful size, I need to fine-tune widths/heighths to have them aligned in a tidy way. To this end, I prefer cropping (clipping mask) them since I was afraif of quality loss by resizing by non-integer factors. Since one needs to see how it looks like (how much I can crop, do sizes look balanced, ...) it is not useful to "calculate" the millimeter dimensions and do the rest in photoshop.