dChord (Function)

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Coordinates
Solid figure
Using the drawing functions
Drawing in PHP
Drawing in Browser code

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dChord (Function)

In french: dCorde

Draws the chord of a circle (intersection between an ellipse and a straight line):

in an Image control,
in a variable of type Image.
This type of variable is not available.
in a variable of type WDPic (on the background layer),
in a variable of type picLayer.

Caution: Using this function under Linux requires a specific configuration.. For more details, see The drawings.

Example

See additional examples

// Initialise le dessin dans un champ Image
dStartDrawing(IMG_Dessin)
// Dessin d'une corde de cercle dont le 
// fond est jaune clair et le bord bleu clair
dChord(10, 10, 50, 50, 20, 20, 40, 50, LightYellow, LightBlue)

// Dessin d'une corde de cercle dont le 
// fond est jaune clair et le bord bleu clair
dChord(IMG_Dessin, 10, 10, 50, 50, 20, 20, 40, 50, LightYellow, LightBlue)

Syntax

Drawing a chord, specifying all the coordinates of the bounding rectangle Hide the details

dChord([<Image>, ] <X1> , <Y1> , <X2> , <Y2> , <X3> , <Y3> , <X4> , <Y4> [, <Background color> [, <Line color>]])

<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 a variable of type Image.
the name of a variable of type WDPic. Only the background layer will be handled.
the name of a variable of type picLayer.
If this parameter is not specified, it is necessary to define the drawing destination with dStartDrawing.

<X1>: Integer

X-coordinate of the upper-left corner of the rectangle containing the circle. These coordinates are expressed in pixels.

<Y1>: Integer

Y-coordinate of the upper-left corner of the rectangle containing the circle. These coordinates are expressed in pixels.

<X2>: Integer

X-coordinate of the lower-right corner of the rectangle containing the circle. These coordinates are expressed in pixels.

<Y2>: Integer

Y-coordinate of the lower-right corner of the rectangle containing the circle. These coordinates are expressed in pixels.

<X3>: Integer

X-coordinate of the start point of the chord. These coordinates are expressed in pixels.

<Y3>: Integer

Y-coordinate of the start point of the chord. These coordinates are expressed in pixels.

<X4>: Integer

X-coordinate of the end point of the chord. These coordinates are expressed in pixels.

<Y4>: Integer

Y-coordinate of the end point of the chord. These coordinates are expressed in pixels.

<Background color>: Integer or constant (optional)

Background color of the chord. This color can correspond to:
an RGB color (returned by RGB),
an HSL color (returned by HSL),
a WLanguage preset color,
a variable of type Color.
If this parameter is not specified, the background color:
is Transparent if dBackground has not been used beforehand,
corresponds to the color specified in the last call to dBackground.

<Line color>: Integer or constant (optional)

Line color for the circle chord. This color can correspond to:
an RGB color (returned by RGB),
an HSL color (returned by HSL),
a WLanguage preset color,
a variable of type Color.
If this parameter is not specified, the line color:
is Transparent if dPen has not been previously used.
For a variable of type Image, the line will be black.
corresponds to the color specified in the last call to dPen.

Drawing a chord using a Rectangle variable Hide the details

dChord([<Image>, ] <Rectangle> , <X3> , <Y3> , <X4> , <Y4> [, <Background color> [, <Line color>]])

<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 a variable of type Image.
the name of a variable of type WDPic. Only the background layer will be handled.
the name of a variable of type picLayer.
If this parameter is not specified, it is necessary to define the drawing destination with dStartDrawing.

<Rectangle>: Rectangle variable

Name of the Rectangle variable that corresponds to the rectangle containing the circle.

<X3>: Integer

X-coordinate of the start point of the chord. These coordinates are expressed in pixels.

<Y3>: Integer

Y-coordinate of the start point of the chord. These coordinates are expressed in pixels.

<X4>: Integer

X-coordinate of the end point of the chord. These coordinates are expressed in pixels.

<Y4>: Integer

Y-coordinate of the end point of the chord. These coordinates are expressed in pixels.

<Background color>: Integer or constant (optional)

Background color of the chord. This color can correspond to:
an RGB color (returned by RGB),
an HSL color (returned by HSL),
a WLanguage preset color,
a variable of type Color.
If this parameter is not specified, the background color:
is Transparent if dBackground has not been used beforehand,
corresponds to the color specified in the last call to dBackground.

<Line color>: Integer or constant (optional)

Line color for the circle chord. This color can correspond to:
an RGB color (returned by RGB),
an HSL color (returned by HSL),
a WLanguage preset color,
a variable of type Color.
If this parameter is not specified, the line color:
is Transparent if dPen has not been previously used.
For a variable of type Image, the line will be black.
corresponds to the color specified in the last call to dPen.

Remarks

Limitations

dChord is not available in anti-aliasing mode (for more details, see the help about dChangeMode).
dChord is not available for a drawing with management of alpha channel (for more details, see the help about dStartDrawing). This function has no effect.

Coordinates

If the start and end points are not located on the outline of the circle (or on the outline of the ellipse), the point taken into account is the intersection between the circle and the line that joins the specified point and the center of the rectangle (which means the center of the circle).

Coordinates are specified with respect to the upper-left corner of the Image control (coordinates: (0,0)).

Solid figure

The dChord function can only be used to draw a chord: contour only or chord area.. To draw a solid figure (portion defined by the center of the circle and the two points on the circle), use dSlice.

Using the drawing functions

The drawing functions can be used according to 2 methods:

Method 1: Using the dDrawingStartfunction
- 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.
    If function dEndDrawing is called in the same process as function dStartDrawing, the drawing will not appear: it will be automatically deleted.
Method 2: Indicate the design destination 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.

Drawing in PHP

In PHP, the drawing functions are based on the graphic library GD. This library is commonly used by the PHP hosting providers 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.

Limitation for function dChord: Opacity defined with function dBackground is not taken into account.

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.

Attention: 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 project description window.
Reminder: To display the project description window, under the "Project" pane, in the "Project" group, click on "Description".

Special case: Drawing in the browser of an Android phone: Browser drawing functions are only available in Android version 3 and higher..

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

Business / UI classification: Neutral code

Component: wd300pnt.dll