Data: request-file i cant get it to work

[riacg]

I just started using rebol today and its been going pretty well, i decided to try to make a program that would ask the user to choose a picture then the program would grayscale it.

This is the code i used:
data: request-file view layout [image load data effect [grayscale]]

anyways i have tried many variations of this code and i always get "image has no value" so i guess im somehow using the data: request-file command wrong.

anyone wanan tell me what im doing wrong?

Edit: sorry i put the wrong error, the program works but all i see is a gray background (not a grayscaled picture but a lack of one lol)

[Graham]

This is a common error by newbies.

The words between the layout [ .. ] are not rebol, but a rebol dialect.  So, the word "load" is not understood.

Futhermore the 'request-file returns a block of files.  You need to pick the first one in that block.

Code:

data: first load request-file view layout [image data effect [grayscale]]

[Anton]

I usually use the /ONLY refinement of REQUEST-FILE to cause it to return only a single file.
Here are some examples, which you can test by pasting straight into the rebol console:

   if file: request-file/keep/only/save/title "Save Layout:" "Save Layout" [
      alert "save-layout"
      ;save-layout file
   ]
   
   ; Save PNG
   if file: request-file/keep/only/save/title "Save a PNG image:" "Save PNG" [
      alert "create-layout and save/png"
      ;save/png file to-image layout create-layout
      ;view/new layout [image (load file)]
   ]
   
and your code I would probably rewrite like:

   if file: request-file/keep/only/title "Load an image:" "Load image" [
      my-image: load file
      either image? my-image [
         view layout [image (my-image)]
      ][
         alert "not an image file!"
         my-image: none
      ]
   ]

or this:

   view center-face layout [
      btn "Load Image" [
         if file: request-file/keep/only/title "Load an image:" "Load image" [
            my-image: load file
            either image? my-image [
               pic/image: my-image
               show pic
            ][
               alert reform ["The selected file did not load as an image:" file]
               my-image: none
            ]
         ]
      ]
      pic: image effect [fit grayscale]
   ]

[Brock]

Yes, the /only refinement will only show the file you selected and not the block returned by the request-file command - as Anton stated.  Graham's response shows you the first item in the block, so the same net effect.  Here's the simple change to your script;
data: request-file/only view layout [image load data effect [grayscale]]

The 'load' of data is not required, but as you can see from Anton's script, using load you will be able to use the image? command to determine if it's an image or not.