dStartDrawing (Function)

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Drawing with management of opacity

dStartDrawing, zoom and automatic scrollbars

Pattern and PHP

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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,
an Image variable.
This type of variable is not available.

Remark: dStartDrawing initializes all the parameters required to create a drawing for a given element.

Example

// Start drawing in the "IMG_ImageDrawing" control
ResDrawing = dStartDrawing(IMG_ImageDrawing)
// Drawings performed in the "IMG_ImageDrawing" control
...
// End of drawing in the "IMG_ImageDrawing" control

dStartDrawing(IMG_Image1)
dFont("Arial", 12, iNormal, 0)
dText(4, 0, "I am writing my text in an Image control!")

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.
Special case:
1 if successful,
0 if an error occurs.

<Image control>: Control name

Name of Image control where the drawing will be performed.

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

Drawing options:
Versions 22 and later
dDisplayAsynchronous
New in version 22
dDisplayAsynchronous
dDisplayAsynchronous
Versions 16 and later
dDisplayManual
New in version 16
dDisplayManual
dDisplayManual
dWithOpacity Allows the opacity to be managed in the different drawing functions used by the Image control. Used for example to create a drawing saved in PNG format with management of alpha layer.
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 drawing. The gridlines are not saved in the image.
This constant is not available.
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.
This constant is not available.

Versions 17 and later

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:
dWithOpacity Allows managing opacity in the different drawing functions used with the variable. Used for example to create a drawing saved in PNG format with management of alpha layer.
dGridlinesOpacity The drawing is displayed over gridlines in order to highlight the transparent or semi-transparent sections of drawing. The gridlines are not saved in the image.
This constant is not available.
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.
This constant is not available.

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

New in version 17

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:
dWithOpacity Allows managing opacity in the different drawing functions used with the variable. Used for example to create a drawing saved in PNG format with management of alpha layer.
dGridlinesOpacity The drawing is displayed over gridlines in order to highlight the transparent or semi-transparent sections of drawing. The gridlines are not saved in the image.
This constant is not available.
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.
This constant is not available.

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

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:
dWithOpacity Allows managing opacity in the different drawing functions used with the variable. Used for example to create a drawing saved in PNG format with management of alpha layer.
dGridlinesOpacity The drawing is displayed over gridlines in order to highlight the transparent or semi-transparent sections of drawing. The gridlines are not saved in the image.
This constant is not available.
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.
This constant is not available.

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. The drawing will not be displayed if dEndDrawing and dStartDrawing are called in the same process: it will be automatically erased.

Drawing with management of opacity

Creating a drawing with management of opacity is used to easily save the images in PNG format with management of Alpha layer.

To save a PNG drawing with management of Alpha layer:

Use the function dStartDrawing. 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: dPixelOpacity is used to find out the opacity of a point.

Use dSaveImagePNG to save your drawing in PNG format with management of alpha layer (opacity).

Limit: In "Management of opacity" mode, dText is limited to the use of True Type fonts.

dStartDrawing, zoom and automatic scrollbars

The option "Automatic scrollbars and zoom", which is available on Image controls, is not compatible with dStartDrawing. If this option is used on the Image control, dStartDrawing freezes the image. The zoom and the scrollbars are also frozen. The standard behavior is restored during the call to dEndDrawing.

Pattern and PHP

In PHP, the drawing functions are based on the graphic library GD. This library is commonly used by the PHP hosting companies and therefore it is always enabled. The version of the GD library must be version 2.0.28 (or later). This library can be downloaded from the PHP site.

To enable (if necessary) this library locally, the following elements are required:

PHP installed.
the PHP.INI file found in the Windows directory must contain the following line: "extension=php_gd2.dll" (instead of ";extension=php_gd2.dll").
the php_gd2.dll file must exist in the directory of PHP extensions. This directory is defined in the PHP.INI file by the "extension_dir" variable.

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: wd260pnt.dll