scale layer to current canvas size photoshop

For whatever it's worth in 2023 (10 years later) —  here's a version of the script that scales the layer from the center while maintaining aspect ratio...

var maintainAspectRatio = true; // set to true to keep aspect ratio

if (app.documents.length > 0) {
    app.activeDocument.suspendHistory('Fit Layer to Canvas', 'FitLayerToCanvas(' + maintainAspectRatio + ')');
}

function FitLayerToCanvas(keepAspect) { // keepAspect: Boolean - optional. Default to false
    var doc = app.activeDocument;
    var layer = doc.activeLayer;

    // Do nothing if the layer is a background or locked
    if (layer.isBackgroundLayer || layer.allLocked || layer.pixelsLocked || layer.positionLocked || layer.transparentPixelsLocked) return;

    // Do nothing if the layer is not a normal artLayer or Smart Object
    if (layer.kind != LayerKind.NORMAL && layer.kind != LayerKind.SMARTOBJECT) return;

    // Store the ruler
    var defaultRulerUnits = app.preferences.rulerUnits;
    app.preferences.rulerUnits = Units.PIXELS;

    var width = doc.width.as('px');
    var height = doc.height.as('px');

    var bounds = app.activeDocument.activeLayer.bounds;
    var layerWidth = bounds[2].as('px') - bounds[0].as('px');
    var layerHeight = bounds[3].as('px') - bounds[1].as('px');

    // Calculate new position to center the layer
    var newX = (width - layerWidth) / 2;
    var newY = (height - layerHeight) / 2;
    
    // Move the layer to the new position
    layer.translate(new UnitValue(newX - layer.bounds[0].as('px'), 'px'), new UnitValue(newY - layer.bounds[1].as('px'), 'px'));

    if (!keepAspect) {
        // Scale the layer to match the canvas
        layer.resize((width / layerWidth) * 100, (height / layerHeight) * 100, AnchorPosition.MIDDLECENTER);
    } else {
        var layerRatio = layerWidth / layerHeight;
        var newWidth = width;
        var newHeight = (newWidth / layerRatio);

        if (newHeight >= height) {
            newWidth = layerRatio * height;
            newHeight = height;
        }

        var resizePercent = newWidth / layerWidth * 100;
        app.activeDocument.activeLayer.resize(resizePercent, resizePercent, AnchorPosition.MIDDLECENTER);
    }

    // Restore the ruler
    app.preferences.rulerUnits = defaultRulerUnits;
}

Mike Hale's script keeps the aspect ratio of the canvas.  If the normal layer or smart object layer has a different aspect ratio than the canvas it will be distorted to fill the canvas. If you do not want to distort the layer appearance and it has a different aspect ratio than the canvas you would need to resize the layer larger than the canvas so the width or height just fills the canvas's width or height where the other size will be larger than the canvas size. Center the layer over the canvas. The document canvas will act like a clipping mask and the layer will look like a centered crop.  If you look lower in this thread you will see I posted the code in 2013.

Hello,

I have successfully used the script written by Michael over the last year and it saved me lots of time on certain jobs.

I want to say a big thank you for it first!

However, I recently switched to a Mac and I'm using Photoshop CC 2014 Version: 2014.0.0 20140508.r.58 2014/05/08:23:59:59  x64

I get an error when I'm trying to run the script and I have no idea what this error is trying to say.

Can you please help?

Thank you!

There is also a quick and easy menu command.

1. Edit / Free transform
2. Drag layer edges in or out to meet canvass edges... (5 steps in all).

Cudos for Hale and Schruber, et al. I wonder if their ingenius var can fix gradient Foreground to transparent.

PS 2014 Foreground to transparent (gradient problems)

You may also need to take into consideration the aspect ratio of the canvas compared to the aspect ratio of the layer to know the proper way to just fill the canvas to how. If the aspect ratios don't match there will be some spill over but it will be masked off by the canvas size,  Here is the code I use compare Aspect ratios from one of my Photo Collage scripts. Note there is and error in CS6 scripting the first line will encounter an internal error if your Photoshop interpolation preference is Adobe's default Bicubic Automatic.  The bug is fixed in Photoshop CC. IMO Bicubic Automatic is not a good general default interpolation setting for Bicubic Sharper seems to be used for down sizing and it works very poorly on images that have been sharpened before.

You need to get the bounds of the canvas and the active layer and compare their aspect ratio. That code I left out. Make sure the layer you want to resize is the current active layer and has pixels. If you use my code that uses  activeDocument.activeLayer.resize... The error you show looks like the layer your resizing might be empty no pixels to interpolate.

var userResampleMethod = app.preferences.interpolation;  // Save interpolation settings
app.preferences.interpolation = ResampleMethod.BICUBIC; // resample interpolation bicubic

if (LWidth/LHeight<SWidth/SHeight) { // Smart Object layer Aspect Ratio less the Canvas area Aspect Ratio
   var percentageChange = ((SWidth/LWidth)*100);  // Resize to canvas area width
   activeDocument.activeLayer.resize(percentageChange,percentageChange,AnchorPosition.MIDDLECENTER);
   }

else {
  var percentageChange = ((SHeight/LHeight)*100); // resize to canvas area height
  activeDocument.activeLayer.resize(percentageChange,percentageChange,AnchorPosition.MIDDLECENTER);
   }

app.preferences.interpolation = userResampleMethod; // Reset interpolation setting

Something like this?

var doc = app.activeDocument;
var layer = doc.activeLayer;
layer.translate(new UnitValue(0-layer.bounds[0].as('px'),'px'), new UnitValue(0-layer.bounds[1].as('px'),'px'));
layer.resize((doc.width.value/(layer.bounds[2]-layer.bounds[0]))*100,(doc.height.value/(layer.bounds[3]-layer.bounds[1]))*100,AnchorPosition.TOPLEFT);