HTML-Leinwand globalCompositeOperation- Eigenschaft
Beispiel
Zeichnen Sie Rechtecke mit zwei verschiedenen globalCompositeOperation-Werten. Rote Rechtecke sind Zielbilder . Blaue Rechtecke sind Quellbilder :
Quelle-über
Ziel vorbei
JavaScript:
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.fillStyle = "red";
ctx.fillRect(20, 20, 75, 50);
ctx.globalCompositeOperation = "source-over";
ctx.fillStyle = "blue";
ctx.fillRect(50, 50, 75, 50);
ctx.fillStyle = "red";
ctx.fillRect(150, 20, 75, 50);
ctx.globalCompositeOperation = "destination-over";
ctx.fillStyle = "blue";
ctx.fillRect(180, 50, 75, 50);
Browser-Unterstützung
Internet Explorer 9, Firefox, Opera, Chrome und Safari unterstützen die globalCompositeOperation-Eigenschaft.
Definition und Verwendung
Die Eigenschaft globalCompositeOperation legt fest oder gibt zurück, wie ein (neues) Quellbild auf ein (vorhandenes) Zielbild gezeichnet wird.
Quellbild = Zeichnungen, die Sie auf der Leinwand platzieren möchten.
Zielbild = Zeichnungen, die bereits auf der Leinwand platziert sind.
Standardwert: | Quelle-über |
---|---|
JavaScript-Syntax: | Kontext .globalCompositeOperation="source-in"; |
Eigenschaftswerte
Value | Description | Play it |
---|---|---|
source-over | Default. Displays the source image over the destination image | |
source-atop | Displays the source image on top of the destination image. The part of the source image that is outside the destination image is not shown | |
source-in | Displays the source image in to the destination image. Only the part of the source image that is INSIDE the destination image is shown, and the destination image is transparent | |
source-out | Displays the source image out of the destination image. Only the part of the source image that is OUTSIDE the destination image is shown, and the destination image is transparent | |
destination-over | Displays the destination image over the source image | |
destination-atop | Displays the destination image on top of the source image. The part of the destination image that is outside the source image is not shown | |
destination-in | Displays the destination image in to the source image. Only the part of the destination image that is INSIDE the source image is shown, and the source image is transparent | |
destination-out | Displays the destination image out of the source image. Only the part of the destination image that is OUTSIDE the source image is shown, and the source image is transparent | |
lighter | Displays the source image + the destination image | |
copy | Displays the source image. The destination image is ignored | |
xor | The source image is combined by using an exclusive OR with the destination image |
Beispiel
Alle globalCompositeOperation-Eigenschaftswerte: