在UIView Xamarin.IOS C#中绘制图像 [英] Draw Image in UIView Xamarin.IOS C#

问题描述

我在资产目录中有一些pdf图像.我不想直接在UIImageView中使用它，而是想使用CGContext在UIView中绘制它.

I have some pdf images in Asset catalog. Instead of directly using this in UIImageView, I want to draw this in my UIView using CGContext.

类似于 Android.Graphic.Drawable-OnDraw()

IOS中是否有替代方法? 还是我可以参考任何样本?

Is there an alternatives for this in IOS? Or is there any samples that i can refer to?

我还想设置此图像的位置-与Android中的 OnMeasure(int width，int height)类似.

I also want to set the position of this image - similar to OnMeasure(int width, int height) in Android.View

(需要-我想动态绘制图像并在UIView中的触摸位置上编辑图像)

(need - I want to dynamically draw images and edit the images on touch positions in UIView)

请有人对此提供指导. 谢谢.

Could someone guide on this please. Thanks.

推荐答案

在UIView子类的Draw(drawRect:)覆盖中，您可以在当前上下文上进行绘制.在此示例中，我们将整个视图涂成红色，然后从视图中心绘制并缩放一个CGImage，尺寸为100x200:

In your UIView subclass's Draw (drawRect:) override, you can draw on the current context. In this example, we paint the entire view red and then draw and scale a CGImage from the center of the view with a size of 100x200:

public override void Draw(CGRect rect)
{
    var context = UIGraphics.GetCurrentContext();

    context.SetFillColor(UIColor.Red.CGColor);
    context.FillRect(rect);

    var cgImage = UIImage.FromFile("face").CGImage;

    var drawImageToRect = new CGRect(rect.Width / 2, rect.Height / 2, 100, 200);
    context.DrawImage(drawImageToRect, cgImage);
}

回复: iOS绘图概念

如果需要混合使用UIKit和CoreGraphics原点，则可以转换原点(请咨询上面的Apple doc链接中的Coordinate Systems and Drawing in iOS):

If you need to mix UIKit and CoreGraphics origins, you can transform the origin (consult the Coordinate Systems and Drawing in iOS in the Apple doc link above):

public override void Draw(CGRect rect)
{
    var context = UIGraphics.GetCurrentContext();
    context.SaveState();
    context.TranslateCTM(0, rect.Height );
    context.ScaleCTM(1, -1);

    context.SetFillColor(UIColor.Red.CGColor);
    context.FillRect(rect);

    var cgImage = UIImage.FromFile("face").CGImage;
    var drawImageToRect = new CGRect(rect.Width / 2, rect.Height / 2, 100, -200);
    context.DrawImage(drawImageToRect, cgImage);

    context.RestoreState();
}

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