...I'm not exactly sure what you mean but there are some Blitz commands that are "fun, but [you should] use with caution!", while another is "quite possibly one of the most useful, yet underdocumented, confusing commands in the Blitz Basic language".
When you say "saves that data as" you might want SaveImage, but if you just want to store it somewhere (besides on the screen or buffer you're working in) you probably really want CreateImage and GrabImage instead.
In your last line, the data of an image is usually referred to in BlitzPlus by use of a "handle". A handle is kind of like a variable that you use to work with images (and sounds and other things you load into your program like images). Under the hood, it gets a number assigned to it, which is how the program knows how to get to it in memory. The particular number assigned doesn't mean anything, unless it is zero in which case there's no image loaded.
You can see if it's non-zero or not by running your program and using the BlitzPlus debugger ... press the button with the red stoplight (upper left of debugger window) while it's running, (or, to get it to stop automatically, might want to add a "Stop" line inside your program code right under the line where you load your image) and expanding the text under the "Locals" or "Globals" on the right side of the debugger.
When you say "saves that data as" you might want SaveImage, but if you just want to store it somewhere (besides on the screen or buffer you're working in) you probably really want CreateImage and GrabImage instead.
In your last line, the data of an image is usually referred to in BlitzPlus by use of a "handle". A handle is kind of like a variable that you use to work with images (and sounds and other things you load into your program like images). Under the hood, it gets a number assigned to it, which is how the program knows how to get to it in memory. The particular number assigned doesn't mean anything, unless it is zero in which case there's no image loaded.
You can see if it's non-zero or not by running your program and using the BlitzPlus debugger ... press the button with the red stoplight (upper left of debugger window) while it's running, (or, to get it to stop automatically, might want to add a "Stop" line inside your program code right under the line where you load your image) and expanding the text under the "Locals" or "Globals" on the right side of the debugger.