dPixelOpacity (Function)

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Drawing in an image with opacity

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dPixelOpacity (Function)

In french: dPixelOpacité

Identifies the opacity of a pixel in an image that supports the Alpha layer. This image can be:

an Image control,
in an Image variable.
This type of variable is not available.
Versions 25 and later
in a WDPic variable (on the background layer),
New in version 25
in a WDPic variable (on the background layer),
in a WDPic variable (on the background layer),
Versions 25 and later
in an picLayer variable.
New in version 25
in an picLayer variable.
in an picLayer variable.

Versions 15 and later

This function is now available for Java applications.

New in version 15

This function is now available for Java applications.

Versions 16 and later

This function is now available for Android applications.

This function is now available in Browser code.

This function is now available for WINDEV applications in Linux.

Caution: A specific configuration is required to use this function in Linux. See The drawings for more details.

New in version 16

This function is now available for Android applications.

This function is now available in Browser code.

This function is now available for WINDEV applications in Linux.

Caution: A specific configuration is required to use this function in Linux. See The drawings for more details.

This function is now available for Android applications.

This function is now available in Browser code.

This function is now available for WINDEV applications in Linux.

Caution: A specific configuration is required to use this function in Linux. See The drawings for more details.

Versions 17 and later

This function is now available for iPhone/iPad applications.

New in version 17

This function is now available for iPhone/iPad applications.

Example

// Identify the opacity of the pixel (15, 25)
// on the "IMG_ImageDrawing" control
ResOpacity = dPixelOpacity(IMG_ImageDrawing, 15, 25)

Syntax

<Result> = dPixelOpacity([<Image>, ] <X coordinate> , <Y coordinate>)

<Result>: Integer

Opacity of specified pixel (included between 0 for transparent and 255 for opaque).

<Image>: Optional control name or optional Image, WDPic or picLayer variable

Image to use. This image can correspond to:
the name of an Image control.
the name of an Image variable.
This type of variable is not available.
Versions 25 and later
the name of an WDPic variable. Only the background layer will be handled.
New in version 25
the name of an WDPic variable. Only the background layer will be handled.
the name of an WDPic variable. Only the background layer will be handled.
Versions 25 and later
the name of an picLayer variable.
New in version 25
the name of an picLayer variable.
the name of an picLayer variable.
If this parameter is not specified, the image handled by dStartDrawing will be used.

<X coordinate>: Integer

Horizontal position of pixel to use.

<Y coordinate>: Integer

Vertical position of pixel to use.

Remarks

Coordinates

Coordinates are given in pixels with respect to the top left corner of the image (coordinates: (0.0)).

To retrieve the position of a mouse click in an Image control, use MouseXPos and MouseYPos.

Using the drawing functions

The drawing functions can be used according to 2 methods:

Method 1: Using dStartDrawing
- dStartDrawing must be called before any other drawing function. dStartDrawing is used to define the element (Image control or variable) to which the drawing functions will be applied.
- When drawing on an Image control:
  - The drawing functions operate on a copy ("bitmap") of the image. You can use the drawing functions of Windows (via API or CallDLL32) but these 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.
Versions 24 and later
Method 2: indicating the drawing target directly in the syntax (via a parameter)
The <Image> parameter is used to specify directly the target of the drawing. dStartDrawing becomes useless. This function must be deleted.
Versions 25 and later
This syntax is now available.
New in version 25
This syntax is now available.
This syntax is now available.
New in version 24
Method 2: indicating the drawing target directly in the syntax (via a parameter)
The <Image> parameter is used to specify directly the target of the drawing. dStartDrawing becomes useless. This function must be deleted.
Versions 25 and later
This syntax is now available.
New in version 25
This syntax is now available.
This syntax is now available.
Method 2: indicating the drawing target directly in the syntax (via a parameter)
The <Image> parameter is used to specify directly the target of the drawing. dStartDrawing becomes useless. This function must be deleted.
Versions 25 and later
This syntax is now available.
New in version 25
This syntax is now available.
This syntax is now available.

Drawing in an image with opacity

To specify that the drawing in the image handles opacity (Alpha layer), use the dStartDrawing function by specifying the constant dWithOpacity.

Drawing in 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.

Versions 16 and later

Drawing in Browser code

Some drawing functions are available in Browser code. The drawing functions in Browser code are based on the HTML 5 standard. More specifically, these functions are based on the "canvas" tag of HTML 5.

The drawing features in browser code are available for the recent browsers only (supporting the HTML 5 standard). To find out whether the drawing features are proposed by your browser, use DrawingAvailable.

Caution: To use the drawing functions with Internet Explorer 9, the project must include the reference to the DTD file. To do so, the HTML mode must be "HTML 4.01 Transitional + DTD". This option is available in the "Advanced" tab of the description window of project.
Reminder: To open the project description window, on the "Project" pane, in the "Project" group, click "Description".

Special case: Drawing in the browser of an Android phone: The browser drawing functions are only available starting with version 3 of Android.

New in version 16

Drawing in Browser code

Special case: Drawing in the browser of an Android phone: The browser drawing functions are only available starting with version 3 of Android.

Drawing in Browser code

Special case: Drawing in the browser of an Android phone: The browser drawing functions are only available starting with version 3 of Android.

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