4.5 Save Bitmap Example

The SaveBitmap (section 2.2.2.2.1.1.2.12) Primary Drawing Order is used to encode a rectangular screen image for saving or restoring by the client.

The following diagram shows how a 127-by-134-pixel virtual desktop rectangle received in the SaveBitmap Primary Drawing Order is tiled into the client-side Save Bitmap (section 3.2.1.2), and how the position of the next bitmap can be computed.

Figure 20: Illustration of Save Bitmap Primary Drawing Order

Applying the formulas in section 2.2.2.2.1.1.2.12 (assuming an X granularity of 1 and a Y granularity of 20):

 AreaWidthInPixels 
 = [(width + XGranularity - 1) / XGranularity] * XGranularity
 = [(127 + 1 - 1) / 1] * 1
 = 127
  
 AreaHeightInPixels 
 = [(height + YGranularity - 1) / YGranularity] * YGranularity
 = [(134 + 20 - 1) / 20] * 20
 = 140
  
 Area 
 = AreaWidthInPixels * AreaHeightInPixels
 = 127 * 140
 = 17780

Hence, the area occupied by the 127-by-134-pixel bitmap in the SaveBitmap is 17,780 pixels. The X and Y position in the Save Bitmap from which to tile the next bitmap is computed using the formulas in section 2.2.2.2.1.1.2.12.

 Y 
 = [SaveBitmapPosition / (480 * YGranularity)] * YGranularity
 = [17780 / (480 * 20)] * 20
 = 20
  
 X 
 = [SaveBitmapPosition - (Y * 480)] / YGranularity
 = [17780 - (20 * 480)] / 20
 = 409