unity源碼解析Texture2D

遊戲中圖形的表現大多來自於紋理，紋理使用最多的是Texture2D，Texture2D繼承自Texture，Texture裏面大多是對紋理的一些參數的設置，那些設置對於2d3d紋理是通用的，本篇就來看看texture2D具體是如何工作的。

using System;
using System.Runtime.CompilerServices;
using UnityEngine.Internal;

namespace UnityEngine
{
    public sealed class Texture2D : Texture
    {

獲取紋理的級數，這個級數首先是開啓了mipmap，讀取一張圖片時，計算機會生成多張紋理，根據觀察者與物體的遠近選擇不同的紋理。
        public extern int mipmapCount
        {
            [WrapperlessIcall]
            [MethodImpl(MethodImplOptions.InternalCall)]
            get;
        }
獲取紋理格式，比如RGBA32什麼的
        public extern TextureFormat format
        {
            [WrapperlessIcall]
            [MethodImpl(MethodImplOptions.InternalCall)]
            get;
        }
這是一個靜態方法，獲取一個純白色的紋理，測試了一下，該紋理的尺寸爲（0.3,0.3）
        public static extern Texture2D whiteTexture
        {
            [WrapperlessIcall]
            [MethodImpl(MethodImplOptions.InternalCall)]
            get;
        }
也是個靜態方法，獲取一個純黑色紋理，注意的是透明度也是0
        public static extern Texture2D blackTexture
        {
            [WrapperlessIcall]
            [MethodImpl(MethodImplOptions.InternalCall)]
            get;
        }
創建一個自定義尺寸的紋理，當然其他都是默認值
        public Texture2D(int width, int height)
        {
            Texture2D.Internal_Create(this, width, height, TextureFormat.ARGB32, true, false, IntPtr.Zero);
        }
通過限制尺寸，像素格式，是否多級別紋理來創建一個紋理
        public Texture2D(int width, int height, TextureFormat format, bool mipmap)
        {
            Texture2D.Internal_Create(this, width, height, format, mipmap, false, IntPtr.Zero);
        }
通過限制尺寸，像素格式，是否多級別紋理，是否使用線性濾波方式來創建一個紋理
        public Texture2D(int width, int height, TextureFormat format, bool mipmap, bool linear)
        {
            Texture2D.Internal_Create(this, width, height, format, mipmap, linear, IntPtr.Zero);
        }
與上面的創建方式不一樣的地方是，傳入了一個本地的紋理，利用本地紋理創建一個新的紋理，而這個nativeTex可以通過Texture中GetNativeTextureID獲得
        internal Texture2D(int width, int height, TextureFormat format, bool mipmap, bool linear, IntPtr nativeTex)
        {
            Texture2D.Internal_Create(this, width, height, format, mipmap, linear, nativeTex);
        }

        [WrapperlessIcall]
        [MethodImpl(MethodImplOptions.InternalCall)]
        private static extern void Internal_Create([Writable] Texture2D mono, int width, int height, TextureFormat format, bool mipmap, bool linear, IntPtr nativeTex);

        public static Texture2D CreateExternalTexture(int width, int height, TextureFormat format, bool mipmap, bool linear, IntPtr nativeTex)
        {
            return new Texture2D(width, height, format, mipmap, linear, nativeTex);
        }
利用紋理id來更新當前紋理
        [WrapperlessIcall]
        [MethodImpl(MethodImplOptions.InternalCall)]
        public extern void UpdateExternalTexture(IntPtr nativeTex);
設置紋理中指定座標的顏色值，注意之後必須調用apply才起作用
        public void SetPixel(int x, int y, Color color)
        {
            Texture2D.INTERNAL_CALL_SetPixel(this, x, y, ref color);
        }

        [WrapperlessIcall]
        [MethodImpl(MethodImplOptions.InternalCall)]
        private static extern void INTERNAL_CALL_SetPixel(Texture2D self, int x, int y, ref Color color);
獲取像素值
        [WrapperlessIcall]
        [MethodImpl(MethodImplOptions.InternalCall)]
        public extern Color GetPixel(int x, int y);
通過uv座標值獲取像素
        [WrapperlessIcall]
        [MethodImpl(MethodImplOptions.InternalCall)]
        public extern Color GetPixelBilinear(float u, float v);

        [ExcludeFromDocs]
        public void SetPixels(Color[] colors)
        {
            int miplevel = 0;
            this.SetPixels(colors, miplevel);
        }

        public void SetPixels(Color[] colors, [DefaultValue("0")] int miplevel)
        {
            int num = this.width >> miplevel;
            if (num < 1)
            {
                num = 1;
            }
            int num2 = this.height >> miplevel;
            if (num2 < 1)
            {
                num2 = 1;
            }
            this.SetPixels(0, 0, num, num2, colors, miplevel);
        }

        [WrapperlessIcall]
        [MethodImpl(MethodImplOptions.InternalCall)]
        public extern void SetPixels(int x, int y, int blockWidth, int blockHeight, Color[] colors, [DefaultValue("0")] int miplevel);

        [ExcludeFromDocs]
        public void SetPixels(int x, int y, int blockWidth, int blockHeight, Color[] colors)
        {
            int miplevel = 0;
            this.SetPixels(x, y, blockWidth, blockHeight, colors, miplevel);
        }

        [WrapperlessIcall]
        [MethodImpl(MethodImplOptions.InternalCall)]
        public extern void SetPixels32(Color32[] colors, [DefaultValue("0")] int miplevel);

        [ExcludeFromDocs]
        public void SetPixels32(Color32[] colors)
        {
            int miplevel = 0;
            this.SetPixels32(colors, miplevel);
        }
通過讀取文件數據來加載紋理數據
        [WrapperlessIcall]
        [MethodImpl(MethodImplOptions.InternalCall)]
        public extern bool LoadImage(byte[] data);
通過讀取文件數據來加載紋理數據
        [WrapperlessIcall]
        [MethodImpl(MethodImplOptions.InternalCall)]
        public extern void LoadRawTextureData(byte[] data);

        [ExcludeFromDocs]
        public Color[] GetPixels()
        {
            int miplevel = 0;
            return this.GetPixels(miplevel);
        }

        public Color[] GetPixels([DefaultValue("0")] int miplevel)
        {
            int num = this.width >> miplevel;
            if (num < 1)
            {
                num = 1;
            }
            int num2 = this.height >> miplevel;
            if (num2 < 1)
            {
                num2 = 1;
            }
            return this.GetPixels(0, 0, num, num2, miplevel);
        }

        [WrapperlessIcall]
        [MethodImpl(MethodImplOptions.InternalCall)]
        public extern Color[] GetPixels(int x, int y, int blockWidth, int blockHeight, [DefaultValue("0")] int miplevel);

        [ExcludeFromDocs]
        public Color[] GetPixels(int x, int y, int blockWidth, int blockHeight)
        {
            int miplevel = 0;
            return this.GetPixels(x, y, blockWidth, blockHeight, miplevel);
        }

        [WrapperlessIcall]
        [MethodImpl(MethodImplOptions.InternalCall)]
        public extern Color32[] GetPixels32([DefaultValue("0")] int miplevel);

        [ExcludeFromDocs]
        public Color32[] GetPixels32()
        {
            int miplevel = 0;
            return this.GetPixels32(miplevel);
        }

        [WrapperlessIcall]
        [MethodImpl(MethodImplOptions.InternalCall)]
        public extern void Apply([DefaultValue("true")] bool updateMipmaps, [DefaultValue("false")] bool makeNoLongerReadable);

        [ExcludeFromDocs]
        public void Apply(bool updateMipmaps)
        {
            bool makeNoLongerReadable = false;
            this.Apply(updateMipmaps, makeNoLongerReadable);
        }

        [ExcludeFromDocs]
        public void Apply()
        {
            bool makeNoLongerReadable = false;
            bool updateMipmaps = true;
            this.Apply(updateMipmaps, makeNoLongerReadable);
        }
重新設定紋理參數
        [WrapperlessIcall]
        [MethodImpl(MethodImplOptions.InternalCall)]
        public extern bool Resize(int width, int height, TextureFormat format, bool hasMipMap);

        public bool Resize(int width, int height)
        {
            return this.Internal_ResizeWH(width, height);
        }

        [WrapperlessIcall]
        [MethodImpl(MethodImplOptions.InternalCall)]
        private extern bool Internal_ResizeWH(int width, int height);
決定紋理的質量
        public void Compress(bool highQuality)
        {
            Texture2D.INTERNAL_CALL_Compress(this, highQuality);
        }

        [WrapperlessIcall]
        [MethodImpl(MethodImplOptions.InternalCall)]
        private static extern void INTERNAL_CALL_Compress(Texture2D self, bool highQuality);
傳進來一個紋理集合，把多個紋理打包爲當前紋理
        [WrapperlessIcall]
        [MethodImpl(MethodImplOptions.InternalCall)]
        public extern Rect[] PackTextures(Texture2D[] textures, int padding, [DefaultValue("2048")] int maximumAtlasSize, [DefaultValue("false")] bool makeNoLongerReadable);
傳進來一個紋理集合，把多個紋理打包爲當前紋理
        [ExcludeFromDocs]
        public Rect[] PackTextures(Texture2D[] textures, int padding, int maximumAtlasSize)
        {
            bool makeNoLongerReadable = false;
            return this.PackTextures(textures, padding, maximumAtlasSize, makeNoLongerReadable);
        }
傳進來一個紋理集合，把多個紋理打包爲當前紋理
        [ExcludeFromDocs]
        public Rect[] PackTextures(Texture2D[] textures, int padding)
        {
            bool makeNoLongerReadable = false;
            int maximumAtlasSize = 2048;
            return this.PackTextures(textures, padding, maximumAtlasSize, makeNoLongerReadable);
        }

        public void ReadPixels(Rect source, int destX, int destY, [DefaultValue("true")] bool recalculateMipMaps)
        {
            Texture2D.INTERNAL_CALL_ReadPixels(this, ref source, destX, destY, recalculateMipMaps);
        }

        [ExcludeFromDocs]
        public void ReadPixels(Rect source, int destX, int destY)
        {
            bool recalculateMipMaps = true;
            Texture2D.INTERNAL_CALL_ReadPixels(this, ref source, destX, destY, recalculateMipMaps);
        }

        [WrapperlessIcall]
        [MethodImpl(MethodImplOptions.InternalCall)]
        private static extern void INTERNAL_CALL_ReadPixels(Texture2D self, ref Rect source, int destX, int destY, bool recalculateMipMaps);

        [WrapperlessIcall]
        [MethodImpl(MethodImplOptions.InternalCall)]
        public extern byte[] EncodeToPNG();

        [WrapperlessIcall]
        [MethodImpl(MethodImplOptions.InternalCall)]
        public extern byte[] EncodeToJPG(int quality);

        public byte[] EncodeToJPG()
        {
            return this.EncodeToJPG(75);
        }
    }
}