Unity Texture Texture2D RenderTexture

http://fargesportfolio.com/unity-texture-texture2d-rendertexture/

(1) Texture 基于GPU

(2) RenderTexture基于GPU

(3)Texture2D基于CPU      Texture2D.Apply将CPU数据传递给GPU

------------------------------------------------------------------------2020年4月20更---------------------------------------------------------------------------

这里说一下 Texture2D的Apply操作,当我们使用SetPixel或SetPixels一定要调用Apply方法,不然显示的还是原来的图,这里有个链接具体看下:https://blog.csdn.net/carefreeq/article/details/52635524

图片存在内存中,CPU指向这个图片地址,GPU根据CPU拿过来的地址来显示,如果更改了图片数据,没用调用Apply. 那么GPU没用接收到CPU发来的指令就不会更改这个图的显示.下面的代码,当我没调用Apply的操作时,显示的还是原图,当我调用之后显示的就是纯红色了

 private void BtnClick()
    {
        Texture2D tex = new Texture2D(0, 0);
        tex.LoadImage(File.ReadAllBytes(desktopPath + "/111.jpg"));
        Color[] colors = tex.GetPixels();
        for (int i = 0; i < colors.Length; i++)
            colors[i] = Color.red;

        tex.SetPixels(colors);
        //tex.Apply();  这里更改
        rawImg.texture = tex;
    }

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/// Pass a GPU RenderTexture to CPU Texture2D
/// This opperation has heavy cost (ReadPixels)
/// We reduice the RenderTexture size first to be more efficient
 
void RenderTextureToTexture2D()
{
 
	// Please, be power of 2 for performance issue (2, 4, 8, ...)
	int downSize = 2;
 
	RenderTexture textureToDownsizeAndCopyToCPU = new RenderTexture(1920, 1080, 0);
	Texture2D newTexture2DToBeLoadedTo = new Texture2D(textureToDownsizeAndCopyToCPU.width / downSize, textureToDownsizeAndCopyToCPU.height / downSize, TextureFormat.ARGB32, false);
 
	// Load textureToDownsizeAndCopyToCPU from something you like...
 
	// Create a temporary downsized texture
	RenderTexture textureDownsized = RenderTexture.GetTemporary(textureToDownsizeAndCopyToCPU.width / downSize, textureToDownsizeAndCopyToCPU.height / downSize);
 
	// Remember currently active render texture
	RenderTexture currentActiveRT = RenderTexture.active;
 
	RenderTexture.active = textureDownsized;
 
	// Copy textureToDownsizeAndCopyToCPU to textureDownsized
	Graphics.Blit(textureToDownsizeAndCopyToCPU, textureDownsized);
 
	// Read the RenderTexture image into it
	// Pass GPU bytes to CPU
        // Very performance consuming
	newTexture2DToBeLoadedTo.ReadPixels(new Rect(0, 0, textureDownsized.width, textureDownsized.height), 0, 0, false);
	// Debug.Log(tex2D.width + " " + tex2D.height);
	// Restorie previously active render texture
	RenderTexture.active = currentActiveRT;
 
	RenderTexture.ReleaseTemporary(textureDownsized);
}
 
 
void RenderTextureFromShader()
{
        Graphics.Blit(null, RenderTextureDestination, materialShader);
}

 

1: 赋值图片是灰色

Graphics.CopyTexture（或Graphics.Blit）在GPU端工作，而ReadPixels在CPU上工作。这就是为什么CPU上的EncodetoJPG在ReadPixels而不是CopyTexture之后工作的原因。

您必须使用此程序将JPG保存到磁盘

https://answers.unity.com/questions/1479723/encodetojpg-creates-gray-image-after-using-copytex.html

2:将RenderTexture转换为Texture2D

RenderTexture.active = myRenderTexture;
myTexture2D.ReadPixels(new Rect(0, 0, myRenderTexture.width, myRenderTexture.height), 0, 0);
myTexture2D.Apply();

3:Texture2D到RenderTexture

 // texRef is your Texture2D
 // You can also reduice your texture 2D that way
    RenderTexture rt = new RenderTexture(texRef.width / 2, texRef.height / 2, 0);
    RenderTexture.active = rt;
    // Copy your texture ref to the render texture
    Graphics.Blit(texRef, rt);
         
    // Now you can read it back to a Texture2D if you care
    if (tex2D == null)
         tex2D = new Texture2D(rt.width, rt.height, TextureFormat.RGBA32, true);
    tex2D.ReadPixels(new Rect(0, 0, rt.width, rt.height), 0, 0, false);