在PlayN中以编程方式淡入图像 [英] Programmatically fading in an image in PlayN

问题描述

我正在使用PlayN进行游戏，在某处我想拍摄图像(当前为PNG格式，已经有8位Alpha)，并且我想将图像乘以额外的alpha因子，基于我的代码中的值.

I'm working on a game using PlayN, and there's a bit where I would like to take an image (which is currently in PNG format, with 8-bit alpha already) and I would like to multiply the image by an additional alpha factor, based on a value from my code.

具体来说，我有一张当前生活在ImageLayer中的脸的图片，而我想要的效果是拥有这样的东西:

Specifically, I have a picture of a face that currently lives in an ImageLayer, and the effect that I would like would be to have something like this:

void init() {
  faceImage = assetManager().getImage("images/face.png");
  graphics().rootLayer().add(faceImage);
}

void update(float deltaMilliseconds) {
  // start at fully transparent, fade to fully opaque 
  float transparency = calcTransparency(deltaMilliseconds);
  faceImage.setTransparency(transparency);
}

我希望有一些方法可以对GroupLayers和混合模式进行一些棘手的操作，也许可以将图像与CanvasLayer混合在一起，该CanvasLayer涂有由我的代码控制透明度的纯白色矩形，但是对于我来说，这不是最好的方法实现看似很普通的效果.

I expect that there's some way to do some trickiness with GroupLayers and blend modes, perhaps blending the image with a CanvasLayer painted with a solid white rectangle with transparency controlled by my code, but it's not obvious to me if that's the best way to achieve what seems like a pretty common effect.

推荐答案

如果您只想将图像从完全透明变淡为完全不透明，则只需执行以下操作:

If you just want to fade the image in from fully-transparent to fully-opaque, then just do the following:

ImageLayer faceLayer;
void init() {
  Image faceImage = assetManager().getImage("images/face.png");
  faceLayer = graphics().createImageLayer(faceImage);
  graphics().rootLayer().add(faceLayer);
}

void update(float delta) {
  float alpha = calcAlpha(delta);
  faceLayer.setAlpha(alpha);
}

alpha范围从0(完全透明)到1(完全不透明).

Where alpha ranges from 0 (fully transparent) to 1 (fully opaque).

这篇关于在PlayN中以编程方式淡入图像的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！