Help me get better at Swift

gistfile1.swift

    
    func rangeOfPixelsForRow(row: Int) -> Range<Int>
    {
        return row * imageSize.width..(row+1)*imageSize.width
    }
    
    func rangeOfPixelsForColumn(column: Int) -> StridedRangeGenerator<Int>
    {
        return (column..imageSize.height*imageSize.width).by(imageSize.width)
    }
    
    func indicesOfEdgePixels(inset: Int) -> Array<Int>
    {
        var indices = Int[]()
        
        for pixelIndex in rangeOfPixelsForRow(0)
        {
            indices.append(pixelIndex)
        }
        
        for pixelIndex in rangeOfPixelsForRow(imageSize.height-1)
        {
            indices.append(pixelIndex)
        }
        
        for pixelIndex in rangeOfPixelsForColumn(0)
        {
            indices.append(pixelIndex)
        }
        
        for pixelIndex in rangeOfPixelsForColumn(imageSize.width-1)
        {
            indices.append(pixelIndex)
        }
        
        return indices
    }
    

There's currently a bug where this code double counts corner pixels, but my main questions are:

• Is there a more concise way to merge a few ranges?
• Why can I return a simple Range from the row method, but need to return a generator from the column method?
• Is there anything else wrong with this code?