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Metodo Graphics.DrawImage (Image, Rectangle, Single, Single, Single, Single, GraphicsUnit, ImageAttributes, Graphics.DrawImageAbort, IntPtr)

 

Data di pubblicazione: ottobre 2016

Disegna la parte specificata dell'oggetto Image specificato nella posizione e con le dimensioni specificate.

Spazio dei nomi:   System.Drawing
Assembly:  System.Drawing (in System.Drawing.dll)

public void DrawImage(
	Image image,
	Rectangle destRect,
	float srcX,
	float srcY,
	float srcWidth,
	float srcHeight,
	GraphicsUnit srcUnit,
	ImageAttributes imageAttrs,
	Graphics.DrawImageAbort callback,
	IntPtr callbackData
)

Parametri

image
Type: System.Drawing.Image

Oggetto Image da disegnare.

destRect
Type: System.Drawing.Rectangle

Struttura Rectangle che specifica la posizione e le dimensioni dell'immagine disegnata. L'immagine viene adattata al rettangolo.

srcX
Type: System.Single

Coordinata X dell'angolo superiore sinistro della parte dell'immagine di origine da disegnare.

srcY
Type: System.Single

Coordinata Y dell'angolo superiore sinistro della parte dell'immagine di origine da disegnare.

srcWidth
Type: System.Single

Larghezza della parte dell'immagine di origine da disegnare.

srcHeight
Type: System.Single

Altezza della parte dell'immagine di origine da disegnare.

srcUnit
Type: System.Drawing.GraphicsUnit

Membro dell'enumerazione GraphicsUnit che specifica le unità di misura usate per determinare il rettangolo di origine.

imageAttrs
Type: System.Drawing.Imaging.ImageAttributes

Oggetto ImageAttributes che specifica le informazioni di ricolorazione e gamma per l'oggetto image.

callback
Type: System.Drawing.Graphics.DrawImageAbort

Delegato Graphics.DrawImageAbort che specifica un metodo da chiamare durante il disegno dell'immagine. Questo metodo viene chiamato frequentemente per controllare se sia necessario interrompere l'esecuzione del metodo DrawImage secondo i criteri determinati dall'applicazione.

callbackData
Type: System.IntPtr

Valore che specifica ulteriori dati per il delegato Graphics.DrawImageAbort da usare quando si verifica se interrompere l'esecuzione del metodo DrawImage.

Exception Condition
ArgumentNullException

image è null.

The srcX, srcY, srcWidth, and srcHeight parameters specify a rectangular portion, of the image object to draw. The rectangle is relative to the upper-left corner of the source image. This portion is scaled to fit inside the rectangle specified by the destRect parameter.

This overload with the callback and callbackData parameters provides the means to stop the drawing of an image once it starts according to criteria and data determined by the application. For example, an application could start drawing a large image and the user might scroll the image off the screen, in which case the application could stop the drawing.

The following code example is designed for use with Windows Forms, and it requires T:System.Windows.Forms.PaintEventArgse, which is a parameter of the E:System.Windows.Forms.Control.Paint event handler. The code first defines a callback method for the T:System.Drawing.Graphics.DrawImageAbort delegate; the definition is simplistic and merely tests to see whether the M:System.Drawing.Graphics.DrawImage(System.Drawing.Image,System.Drawing.Rectangle,System.Single,System.Single,System.Single,System.Single,System.Drawing.GraphicsUnit,System.Drawing.Imaging.ImageAttributes,System.Drawing.Graphics.DrawImageAbort,System.IntPtr) method calls it with a null callBackData parameter. The main body of the example performs the following actions:

  • Creates an instance of the T:System.Drawing.Graphics.DrawImageAbort callback method.

  • Creates an image from a JPEG file SampImag.jpg in the folder of the example.

  • Creates points that define a destination rectangle in which to draw the image.

  • Creates a source rectangle to select the portion of the image to draw.

  • Sets the graphics drawing unit to pixel.

  • Draws the original image to the screen.

  • Creates an additional destination rectangle in which to draw an adjusted image.

  • Creates and sets the attributes of the adjusted image to have a larger-than-usual gamma value.

  • Draws the adjusted image to the screen.

For the original, unadjusted destination rectangle, the position locates the image on the screen, and the size of the source rectangle and the size and shape of the destination rectangle determines the scaling of the drawn image.

Because this example uses an overload that passes a callBackData parameter, the T:System.Drawing.Graphics.DrawImageAbort callback returns false, which causes the M:System.Drawing.Graphics.DrawImage(System.Drawing.Image,System.Drawing.Rectangle,System.Single,System.Single,System.Single,System.Single,System.Drawing.GraphicsUnit,System.Drawing.Imaging.ImageAttributes,System.Drawing.Graphics.DrawImageAbort,System.IntPtr) method to continue, and the example draws the adjusted image to the screen.


// Define DrawImageAbort callback method.
private bool DrawImageCallback8(IntPtr callBackData)
{

    // Test for call that passes callBackData parameter.
    if(callBackData==IntPtr.Zero)
    {

        // If no callBackData passed, abort DrawImage method.
        return true;
    }
    else
    {

        // If callBackData passed, continue DrawImage method.
        return false;
    }
}
public void DrawImageRect4FloatAttribAbortData(PaintEventArgs e)
{

    // Create callback method.
    Graphics.DrawImageAbort imageCallback
        = new Graphics.DrawImageAbort(DrawImageCallback8);
    IntPtr imageCallbackData = new IntPtr(1);

    // Create image.
    Image newImage = Image.FromFile("SampImag.jpg");

    // Create rectangle for displaying original image.
    Rectangle destRect1 = new Rectangle(100, 25, 450, 150);

    // Create coordinates of rectangle for source image.
    float x = 50.0F;
    float y = 50.0F;
    float width = 150.0F;
    float height = 150.0F;
    GraphicsUnit units = GraphicsUnit.Pixel;

    // Draw original image to screen.
    e.Graphics.DrawImage(newImage, destRect1, x, y, width, height, units);

    // Create rectangle for adjusted image.
    Rectangle destRect2 = new Rectangle(100, 175, 450, 150);

    // Create image attributes and set large gamma.
    ImageAttributes imageAttr = new ImageAttributes();
    imageAttr.SetGamma(4.0F);

    // Draw adjusted image to screen.
    try
    {
        checked
        {

            // Draw adjusted image to screen.
            e.Graphics.DrawImage(
                newImage,
                destRect2,
                x, y,
                width, height,
                units,
                imageAttr,
                imageCallback,
                imageCallbackData);
        }
    }
    catch (Exception ex)
    {
        e.Graphics.DrawString(
            ex.ToString(),
            new Font("Arial", 8),
            Brushes.Black,
            new PointF(0, 0));
    }
}

.NET Framework
Disponibile da 1.1
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