OpenLayer Offline Manual

OpenLayer | Canvas | SetPixelWriteMode SetPixelWriteMode Advanced function
static void SetPixelWriteMode( | PixelWriteMode mode )
Selects which color components of the Canvas the rendering functions affect. Possible choises are: COLOR_AND_ALPHA - Both the color value and alpha channel are affected (Default for Bitmaps) COLOR_ONLY - Only the color values are affected (Default for the screen) ALPHA_ONLY - Only the alpha channel is affected If you wish to alter the alpha channel of a Bitmap, for example, you can set the Bitmap as the active canvas and set the pixel write mode to ALPHA_ONLY. Examples // Select a Bitmap as the active Canvas // Bitmap bmp( ... ); Canvas::SetTo( bmp ); // Make the rendering functions to affect the alpha channel of the Bitmap // Canvas::SetPixelWriteMode( ALPHA_ONLY ); // Make the rendering functions to affect only the color channels (the default option) // Canvas::SetPixelWriteMode( COLOR_ONLY ); Other functions of the class Canvas
SetTo | Selects the active rendering surface
Refresh | Refresh the contents of the active rendering surface
Fill | Fills the active rendering surface with the specified color
SetClipping | Sets the clipping region of the active rendering surface
DisableClipping | Disables the clipping region
GetClippingRegion | GetClippingRegion
Width | Returns the width of the active rendering surface
Height | Returns the height of the active rendering surface
Save | Saves the contents of the surface to an image file
Advanced functions
SetPixelWriteMode | Selects which color components the rendering functions affect
GetMemoryBitmap | Returns the contents of the Canvas in a memory bitmap
Push | Pushes the active Canvas to a stack
Pop | Pops the most recently stored Canvas from the stack
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