iOSBitmap.Constructor(width As Integer, height As Integer, scale As Double, opaque As Boolean = False)
From Xojo Documentation
Creates a bitmap image using the specified width, height, scale and opaqueness.
Setting opaque to True disables the alpha channel. If you know that you wil be filling every point in the bitmap, set opaque to True to improve performance.
The scale indicates how the image appears on the device. For example, bitmaps drawn with a scale of 1.0 will appear at half the size when drawn on a device with a 2x screen. When creating an iOSBitmap you intend to put on screen, you want your bitmap to have the same scale factor as the screen and the number of pixels in each dimension multiplied by the scale factor. Use the example code on the Declare page to check the device scale.