Y = GetGadgetAttribute(0, #PB_Canvas_MouseY) X = GetGadgetAttribute(0, #PB_Canvas_MouseX) If EventType() = #PB_EventType_LeftButtonDown Or (EventType() = #PB_EventType_MouseMove And GetGadgetAttribute(0, #PB_Canvas_Buttons) & #PB_Canvas_LeftButton) RedoRandomAlphaDrawing(#workingAlphaImageNum) If CreateImage(#workingAlphaImageNum, #canvasW, #canvasH, 32, #White) create working image with alpha (32-bit) this is the 'shadow canvas' where real drawing takes place If OpenWindow(0, 0, 0, #canvasW + 20, #canvasH + 20, "Test Canvas RGBA (alpha in 24bit) v0.2", #PB_Window_SystemMenu | #PB_Window_ScreenCentered)ĬanvasGadget(0, 10, 10, #canvasW, #canvasH, #PB_Canvas_Container) SetGadgetAttribute(0, #PB_Canvas_Image, ImageID(#workingAlphaImageNum)) If IsImage(imageNum) And StartDrawing(ImageOutput(imageNum))īox(0, 0, OutputWidth(), OutputHeight(), #White)īox(29, 49, 222, 222, RGBA(240, 240, 240, 0)) make an area with less alpha to show later blending Procedure redoRandomAlphaDrawing(imageNum) #workingAlphaImageNum = 1 Also known as the 'shadow canvas'. Interactions with the actual canvas is used to reference information on the 'shadow canvas' to obtain RGBA info. Drawing is done to the working alpha image that acts as a 'shadow canvas'. Code: Select all Demnstration of RGBA interaction with a 'shadow canvas' by using a working image with alpha.
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