dStartDrawing (Function)

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Special cases
Drawing with opacity

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dStartDrawing (Function)

In french: dDébutDessin

Indicates that the drawing functions that will be used are intended for:

the specified Image control,
a variable of type Image.

Remark: Function dStartDrawing initializes all parameters required to create (or continue) a drawing for a given element.

Example

// Début du dessin dans le champ Image "IMG_ImageDessin"
ResDessin = dStartDrawing(IMG_ImageDessin)
// Dessins dans le champ Image "IMG_ImageDessin"
...
// Fin des dessins dans le champ Image "IMG_ImageDessin"

dStartDrawing(IMG_Image1)
dFont("Arial", 12, iNormal, 0)
dText(4, 0, "J'écris mon texte dans un champ Image !")

Syntax

Starting a drawing in an Image control Hide the details

<Result> = dStartDrawing(<Image control> [, <Options>])

<Result>: System integer

Memory DC (device context) of the Image control,
0 if an error occurs. This parameter can be used to call system routines (functions of Windows API). In this case, we recommend that you use a system integer.

<Image control>: Control name

Name of Image control where the drawing will be performed.

<Options>: Optional Integer constant (or combination of constants)

Drawing options:
dDisplayAsynchronous
dDisplayManual
dErase
(Default value) Erases the drawing found in the Image control.
dGridlinesOpacity The drawing is displayed over gridlines in order to highlight the transparent or semi-transparent sections of the drawing. The gridlines are not saved in the image.
dNoErase Does not erase the drawing found in the Image control.
dOnChart Used to draw in an Image control in which a chart was already drawn. In this case, the chart drawing is not erased.
dWithOpacity Allows the opacity to be managed in the different drawing functions used by the Image control. Used for example to create a PNG drawing with an Alpha channel.

Starting the drawing in an Image, WDPic or picLayer variable Hide the details

<Result> = dStartDrawing(<Element> [, <Options>])

<Result>: Boolean

True if the drawing was initialized,
False otherwise.

<Element>: Image, WDPic or picLayer variable

Name of a variable:
of type Image.

<Options>: Optional Integer constant (or combination of constants)

Drawing options:
dGridlinesOpacity The drawing is displayed over gridlines in order to highlight the transparent or semi-transparent sections of the drawing. The gridlines are not saved in the image.
dNoErase Does not erase the drawing in the variable.
dOnChart Used to draw in a variable in which a chart has already been drawn. In this case, the chart drawing is not erased.
dWithOpacity Allows managing opacity in the different drawing functions used with the variable. Used for example to create a PNG drawing with an Alpha channel.

No drawing option is used if this parameter is not specified.

Remarks

Special cases

dStartDrawing must be called before the other drawing functions. dStartDrawing is used to define the element (Image control or Image variable) onto which the drawing functions will be applied.
When drawing in an Image control:
- the drawing functions operate on a copy ("bitmap") of image. You can use the drawing functions of Windows (via API or CallDLL32) but these Windows functions must use the DC (Device Context) returned by dStartDrawing.
- dEndDrawing and dStartDrawing must not be called in the same process. If function dEndDrawing is called in the same processing as function dStartDrawingfunction, the drawing will not appear: it will be automatically deleted.

Drawing with opacity

By creating a drawing that supports opacity, you can easily save PNG images with an Alpha channel.

To save a PNG drawing with an Alpha channel:

Use the dStartDrawing function. This function is used to define, if necessary, the element onto which the drawing functions will be applied as well as the drawing mode. The dWithOpacity constant is used to indicate that the drawing will manage the opacity. The dGridlinesOpacity constant is used to display gridlines underneath the different drawing areas.

Configure the opacity of your drawings with the following functions:


dBackground	Declares the background color and its opacity for the next drawings.
dPoint	Declares the color of the points and their opacity for the next drawings.
dPen	Declares the color of the lines and their opacity for the next drawings.

Remark: The dPixelOpacity function is used to determine the opacity of a point.

Use dSaveImagePNG to save your drawing in PNG format with alpha channel (opacity).

Limit In "Opacity management" mode, the dText function is limited to the use of TrueType fonts.

Related Examples:

Unit examples (WINDEV): The drawing functions

[ + ] Using the main drawing functions of WINDEV to:
- Initialize an Image control for drawing
- Draw simple shapes
- Write a text into a drawing
- Change the color in a drawing

Component: wd300pnt.dll