This section describes behavior and properties of TCustomImage32 and TImage32 controls, as well as their realization of layers.
Since TCustomImage32 and TImage32 share the same behavior, I will denote both of them here as TImage32. Most of the description applies to the TImgView32 control as well.
Overview
TImage32 is an image displaying visual component, which also holds a collection of layers.
The internal image of the control is a TBitmap32 object. The scale and position of the image within the control’s boundaries can be controlled with several properties. See Bitmap Image for details.
A layers is, generally speaking, an entities which ‘knows’ how to combine itself with the back buffer of the control. TImage32 maintains a collection of layers. See ‘Using Layers‘ for details.
When the image paints itself, it runs through several Paint Stages which determine the order in which layers and the bitmap image are painted. This order is completely customizeable.
To avoid flicker and to speed-up scaling and blending operations, each layer and the bitmap image is painted to a back-buffer of the control. See the reference of TImage32 ancestor TCustomPaintBox32 for details of the back-buffer realization.
Finally, TImage32 supports change notification via the OnChange event, which is done similar to change notification in TBitmap32. Basically, it redirects change notification from its layers and the bitmap image.