Check the canvas against given size requirements and makes the necessary adjustments

CanvasSizeCheck.jsx

// enable double clicking
#target photoshop
app.bringToFront();

var doc = activeDocument;

// Save the current preferences
var startRulerUnits = app.preferences.rulerUnits
var startDisplayDialogs = app.displayDialogs
var startBgColor = app.backgroundColor

// Set Adobe Photoshop CC 2015 to use pixels and display no dialogs
app.preferences.rulerUnits = Units.PIXELS
app.displayDialogs = DialogModes.NO
app.backgroundColor.rgb.hexValue = "ffffff"

var startWidth = doc.width;
var startHeight = doc.height;
var startRes = doc.resolution;
var startProfile = doc.colorProfileName;

var endWidth = 300; 
var endHeight = 200;
var endRes = 72;
var endProfile = "sRGB IEC61966-2.1"

var startRatio = startWidth / startHeight;
var endRatio = endWidth / endHeight;

doc.backgroundLayer.duplicate(); 

if (startRes != endRes){   
    doc.resizeImage(startWidth, startHeight, endRes, ResampleMethod.AUTOMATIC);
}

if (endRatio < startRatio){
    if (endHeight > endWidth){
        doc.resizeCanvas(null, (1 / endRatio) * startHeight, AnchorPosition.MIDDLECENTER);
    } 
} else {
        doc.resizeCanvas(endRatio * startWidth, null, AnchorPosition.MIDDLECENTER);
}

app.activeDocument.convertProfile(endProfile, Intent.RELATIVECOLORIMETRIC, true, true );

// Reset the application preferences
app.preferences.rulerUnits = startRulerUnits
app.displayDialogs = startDisplayDialogs
app.backgroundColor = startBgColor