Step by step instruction - how to change a large file to a specific size

Use the crop too set it to crop aspect ratio 8:1 and drag out your 8:1 image composition, The use menu Image>Images resize or  menu File>Automate>Fit image to resize the crop to 1600x200px.  I do not believe you will be happy with the image composition.

danielledsydney  wrote Hi I have a large image 9,197KB (4928px x 3264 px). I want to crop to 1600 x 200 150 dpi with a file size between 200-300 kb in jpeg.

Lets examine what you have  and want to do.

"I have a large image 9,197KB" That is more or less meaningless for you most likely referring do a file size of some image file format which is most likely data compressed.

"(4928px x 3264 px)" Now that is the Image size you have which  has an aspect ratio of 1.509803921568627 very close to  a standard 3:2 Aspect Ratio image ratio of of 1.5.

You want an image 1600x200px which has aspect tario of 8:1 which is very wide compared  a standard a 3:2 aspect ratio 1.5.   Such a crop would drastically change your image's composition because of the aspect ratio crop.   You would be discarding the majority of your Image's content.

You would be discarding the white areas and keeping the white area on an images depicted here.  It would not be very satisfactory you would be discarding most of you images content.  Are you sure this is what you want to do.  It would be easy to do but IMO not something you would want ti do.

There's not much to it. The downsize option will affect image eventual size.  Bilinear would be a good option, but if you keep the original and work on a copy, you can always go back.

Having downsized the image, Save it as a JPG with a quality setting of 10, and see what the resulting image size is.  If it exceeds 300kb the Save as JPG again, and use a lower quality setting.

Note that JPG compression works better on images with fewer variations on colour.  A solid red will compress to a tiny size, where as a psychedelic mess will save as a much larger file.

[EDIT] Note that my screen shot has Bicubic Sharper highlighted.  Bt all means try that, but it will result in a larger file size than Bilinear.  I also find that Bicubic Sharper is much too harsh and produces an oversharpened end result.