REBOL [
    File: %thumbnail-maker.r
    Date: 4-sep-2009
    Title: "Thumbnail Maker"
    Author:  Nick Antonaccio
    Purpose: {
        Create image preview sheets from a list of files.  Used to make the
        introductory image at http://musiclessonz.com/rebol.html        
    }
]

view center-face layout [
    text "Resize input images to this height:"
    height: field "200"
    text "Create output mosaic of this width:"
    width: field "600"
    text "Space between thumbnails:"
    padding-size: field "30"
    text "Color between thumbnails:"
    btn "Select color" [background-color: request-color/color white]
    text "Thumbnails will be displayed in this order:"
    the-images: area
    across
    btn "Select images" [
        some-images: request-file/title trim/lines {Hold
            down the [CTRL] key to select multiple images:} ""
        if some-images = none [return] 
        foreach single-image some-images [
           append the-images/text single-image
           append the-images/text "^/"
        ]
        show the-images
    ]
    btn "Create Thumbnail Mosaic" [
        y-size: to-integer height/text
        mosaic-size: to-integer width/text
        padding: to-integer padding-size/text
        if error? try [background-color: to-tuple background-color][
            background-color: white
        ]
        images: copy parse/all the-images/text "^/"
        if empty? images [alert "No images selected." break]
        mosaic: compose [
            backcolor (background-color) space (padding) across
        ]
        foreach picture images [
             flash rejoin ["Resizing " picture "..."]
             original: load to-file picture
             unview
             either original/size/2 > y-size [
                 new-x-factor: y-size / original/size/2
                 new-x-size: round original/size/1 * new-x-factor
                 new-image: to-image layout/tight [
                     image original to-pair rejoin [new-x-size "x" y-size]
                 ]
                 append mosaic compose [image (new-image)]
             ][
                 append mosaic compose [image (original)]
             ]
             current-layout: layout/tight mosaic
             if current-layout/size/1 > mosaic-size [
                 insert back back tail mosaic 'return
             ]
        ]
        filename: to-file request-file/file/save "mosaic.png"
        save/png filename (to-image layout mosaic)
        view/new layout [image load filename]
    ]
]