Stretch image in one dimension

Hi all,

Not sure I clearly understood the goal, but it was really exciting to play with the idea.

Here is a first try, and first draft of my AutoFeedSlug script.

function nonZero(/*num*/x,  e)
//----------------------------------------------------------
// EPSILON-aware nonzero test.
{
    e = Math.pow(2,-51);
    return ( 0 > x ? -x : x ) > e;
};
function autoFeedSlug(/*?Image[0]*/img,  pge,rec,side,dpg,snap,edge,a,i,t,s,o)
//----------------------------------------------------------
// Given an Image that should extend up to the slug but has not enough material,
// try to feed the missing area by fitting and rescaling a slice of the picture.
// [REM] The code autodetects the edge of interest, provided the image presents any
// border close to a page edge. (Also, make sure the container has no stroke.)
{
    // Settings and constants.
    // ---
    const SNAP = .05;            // 5% of the lowest page dim.
    const FIT_FACTOR = 2;        // Should be 2 (IMHO) to optimize the joint.
    const PGE=0, REC=1, IMG=2;   // Simple enum.
    // ---
    const CS_SPREAD = +CoordinateSpaces.SPREAD_COORDINATES;
    const BB_GEO = +BoundingBoxLimits.GEOMETRIC_PATH_BOUNDS;
    const RM_MULT = +ResizeMethods.MULTIPLYING_CURRENT_DIMENSIONS_BY;
    const RC_KEEP = +ResizeConstraints.KEEP_CURRENT_VALUE;
    const PS_LEFT = +PageSideOptions.LEFT_HAND;
    const PS_RIGHT = +PageSideOptions.RIGHT_HAND;
    // Checkpoints.
    // ---
    if( FIT_FACTOR <= 1 )
    {
        alert("The FIT_FACTOR setting must be greater than 1.");
    }
    while( (!img) || (1!=img.length) || !((img=img[0]) instanceof Image) )
    {
        if( img.hasOwnProperty('images') && (img=img.images).length && ((img=img[0]) instanceof Image) ) break;
        alert("Select an Image.");
        return;
    }
    if( !(pge=img.properties.parentPage) )
    {
        alert("The Image must be on a page.");
        return;
    }
    if( !((rec=img.parent) instanceof Rectangle) || (0 < rec.properties.strokeWeight) )
    {
        alert("The Image must belong to a rectangular box having no stroke.");
        return;
    }
    // Metrics.
    // => `a` :: [ pageTLBR, recTLBR, imgTLBR ]
    // ---
    for( a=[pge,rec,img], i=PGE ; i <= IMG ; ++i )
    {
        t = a.transformValuesOf(CS_SPREAD)[0].matrixValues;
        if( nonZero(t[0]*t[1]) || nonZero(t[2]*t[3]) )
        {
            alert("No weird rotation should be applied to the "+a.constructor.name+".");
            return;
        }
        a = (t=a.properties[i===PGE?'bounds':'geometricBounds']);
        a.width = t[3]-t[1];
        a.height = t[2]-t[0];
    }
    // Page side.
    // => `side` :: -1_left  |  0_single  |  +1_right
    // ---
    side = +(0 < pge.documentOffset && pge.side);
    side = (side==PS_RIGHT)-(side==PS_LEFT);
    // Bleed.
    // => `dpg` :: [-top,-left, +bot,+right]
    // ---
    t = resolve(pge.toSpecifier().replace(/\/\/.+/,''));
    if( !(t instanceof Document) ) throw "Unable to find the parent document."
    t = t.documentPreferences.properties;
    dpg = t.documentBleedUniformSize ?
        ( (t=t.documentBleedTopOffset), [-t,-t,t,t] ) :
        [
            -t.documentBleedTopOffset,
            -t.documentBleedInsideOrLeftOffset,
            t.documentBleedBottomOffset,
            t.documentBleedOutsideOrRightOffset
        ];
    // Identify the most relevant edge.
    // => edge :: { 0:TLBR-index, dist:num }, -BLEED < dist < SNAP
    // ---
    snap = SNAP*Math.min(a[PGE].width, a[PGE].height);
    for( (edge=[i=-1]).dist=1/0 ; ++i < 4 ; )
    {
        // i :: 0_top ; 1_left ; 2_bot ; 3_right
        // Calculate the algebraic distance.
        // ---
        s = 2 > i ? 1 : -1;
        t = s*(Math[0<s?'max':'min'](a[REC],a[IMG])-a[PGE]);
        // Skip this edge if its distance to page > snap zone.
        // ---
        if( t > snap ) continue;
        
        // Skip this edge if it already reaches the bleed.
        // ---
        if( t <= s*dpg ) continue;
        // Skip this edge if it regards the spine.
        // ---
        if( side && side==2-i ) continue;
        t < edge.dist && (edge[0]=i,edge.dist=t);
    }
    
    if( 0 > (i=edge[0]) )
    {
        alert("Unable to find the relevant edge. Make sure the image is in the snap zone.");
        return;
    }
    
    // ---
    // Process.
    // ---
    
    // First, duplicate the rec applying the proper shift.
    // ---
    edge[0] = edge.dist*(2 > i ? -1 : 1) + dpg;
    edge[(1&i)?'push':'unshift'](0);
    t = rec.duplicate(void 0,edge);
    
    // Make sure autofit is off.
    // ---
    t.hasOwnProperty('frameFittingOptions') && t.clearFrameFittingOptions();
    
    // Adjust the geometric bounds.
    // ---
    o = t.geometricBounds;
    o = a[PGE]+dpg;
    o[2^i] = o-FIT_FACTOR*edge[1-(1&i)];
    t.geometricBounds = o;
    
    // Resize the inner image to fit.
    // ---
    img = t.images[0].getElements()[0];
    
    // Ok this step is a bit hacky, but basically
    // we want an anchor point in the form [u,v].
    // i==0  -->  [u,v]==[.5,0]  i.e center-TOP
    // i==1  -->  [u,v]==[0,.5]  i.e LEFT-center
    // i==2  -->  [u,v]==[.5,1]  i.e center-BOTTOM
    // i==3  -->  [u,v]==[1,.5]  i.e RIGHT-center
    // ---
    // It is important to resolve the location of
    // of that anchor relative to the container `t`,
    // not relative to the image bounding box, for
    // the image area may exceed the area of its
    // container! We must use the correct origin
    // in the resize transformation.
    // ---
    (ap=[.5])[(1&i)?'unshift':'push'](+(i>1));
    ap = t.resolve([ap,BB_GEO,CS_SPREAD],CS_SPREAD)[0];
    // Why do I use `resize()`? Because I'm not definitely
    // sure that 90 or 180 angles and/or reflections
    // applied to either the frame or the image couldn't
    // make fail naive methods. Resizing is reliable.
    // ---
    (a=[RC_KEEP])[(1&i)?'unshift':'push'](FIT_FACTOR);
    img.resize(
        CS_SPREAD,        // In-spread bounding box of the Image.
        [ap,CS_SPREAD],   // Origin as computed above (in the spread space)
        RM_MULT,          // Multiply the size by FIT_FACTOR...
        a);               // ...along the desired dimension.
    app.select(null);
};
app.doScript("autoFeedSlug(app.properties.selection)",
    ScriptLanguage.JAVASCRIPT,void 0,UndoModes.ENTIRE_SCRIPT,"AutoFeedSlug");

And here is a quick demo (not sure the link works):

AutoFeedSlug - YouTube

Best,

Marc