When I want scale down an image to a particular number of pixels, I use a little spreadsheet I wrote.  It is cumbersome, I have to copy the existing image dimensions into the spreadsheet, then read the output pixel dimensions and transfer that back to the image/scale dialog. Then let photoshop scale the image and save it under a new name.

I would like to figure out how to tell photoshop to create a downscaled image with a given number of pixels, for example 10,000,000 if I need a 10 megapixel image to post. I cannot just enter a fixed dimension in the height and width boxes because all my images are a variety of shapes, so each one needs a different setting.  Then I could automate the thing pretty easily to do a whole raft of images at once.

Do not know how to do this, either by some windows automation, or photoshop special trick. Do you know how?
thank you

There have been ongoing and numerous  complaints about the search feature at iStock. Both customers and contributors have problems with it.  For buyers, the engine tries to upsell from what the client is looking for, in an effort to push expensive Vetta and Agency images.  For contributors, there is the feeling that the match function is constantly being tweaked for the benefit of somebody else. Also, issues with reliability, predictability and over-complication keep getting mentioned. To many, this does not seem like a serious, professionally written search function, it seems like something the marketing department came up with as just another angle and which just keeps getting hacked endlessly.

This need not be the only search engine available. If you look at the html source of an image detail page, there is sufficient information in it to enable an external search engine.  That information is there only to support outside searches. It is not needed by the internal search at all. An independent search engine could be built by some enterprising person or group. It could work following the wishes of by the user, not the agency.

I'm surprised that with all the internet savvy entrepreneurs out there, nobody has indexed iStockphoto's detailed pages and provided a search engine that works the way the user wants it to.  There is probably a way to make money at it, look what Google did with search.