Texture2D.ReadPixels

参数

描述

从当前渲染目标读取像素并将其写入纹理。

此方法从 GPU 上当前活动的渲染目标（例如屏幕、RenderTexture 或 GraphicsTexture）复制一个矩形区域的像素颜色，并将它们写入 CPU 上位于位置 (destX, destY) 的纹理。 Texture.isReadable 必须为 true，并且必须在 ReadPixels 后调用 Apply 以将更改后的像素上传到 GPU。

左下角为 (0, 0)。

ReadPixels 通常很慢，因为此方法会首先等待 GPU 完成所有先前的工作。要更快地复制纹理，请改用以下方法之一

• AsyncGPUReadback.RequestIntoNativeArray 将纹理从 GPU 复制到 CPU。
• Graphics.CopyTexture、CommandBuffer.CopyTexture 或 Graphics.Blit 仅复制 GPU 上的纹理。

渲染目标和纹理必须使用相同的格式，并且该格式必须在设备上同时支持渲染和采样。

您可以在调用 Apply 时自动更新 mipmap，而不是将 recalculateMipMaps 设置为 true。

以下代码示例演示了如何在内置渲染管线中使用 ReadPixels。在可脚本化渲染管线（如通用渲染管线 (URP)）中，Camera.onPostRender 不可用，但您可以以类似的方式使用 RenderPipelineManager.endCameraRendering。

using UnityEngine;

public class ReadPixelsExample : MonoBehaviour
{
    // Set Renderer to a GameObject that has a Renderer component and a material that displays a texture
    public Renderer screenGrabRenderer;

    private Texture2D destinationTexture;
    private bool isPerformingScreenGrab;

    void Start()
    {
        // Create a new Texture2D with the width and height of the screen, and cache it for reuse
        destinationTexture = new Texture2D(Screen.width, Screen.height, TextureFormat.RGB24, false);

        // Make screenGrabRenderer display the texture.
        screenGrabRenderer.material.mainTexture = destinationTexture;

        // Add the onPostRender callback
        Camera.onPostRender += OnPostRenderCallback;
    }

    void Update()
    {
        // When the user presses the Space key, perform the screen grab operation
        if (Input.GetKeyDown(KeyCode.Space))
        {
            isPerformingScreenGrab = true;
        }
    }

    void OnPostRenderCallback(Camera cam)
    {
        if (isPerformingScreenGrab)
        {
            // Check whether the Camera that just finished rendering is the one you want to take a screen grab from
            if (cam == Camera.main)
            {
                // Define the parameters for the ReadPixels operation
                Rect regionToReadFrom = new Rect(0, 0, Screen.width, Screen.height);
                int xPosToWriteTo = 0;
                int yPosToWriteTo = 0;
                bool updateMipMapsAutomatically = false;

                // Copy the pixels from the Camera's render target to the texture
                destinationTexture.ReadPixels(regionToReadFrom, xPosToWriteTo, yPosToWriteTo, updateMipMapsAutomatically);

                // Upload texture data to the GPU, so the GPU renders the updated texture
                // Note: This method is costly, and you should call it only when you need to
                // If you do not intend to render the updated texture, there is no need to call this method at this point
                destinationTexture.Apply();

                // Reset the isPerformingScreenGrab state
                isPerformingScreenGrab = false;
            }
        }
    }

    // Remove the onPostRender callback
    void OnDestroy()
    {
        Camera.onPostRender -= OnPostRenderCallback;
    }
}

其他资源：ImageConversion.EncodeToPNG。