Unity图片优化-Dither算法（RGBA16优化）

古城微笑少年丶 2022-02-13 00:13 245阅读 0赞

在unity开发过程中，游戏图片占用了很大一部分的手机内存。所以在游戏开发中，对图片的优化也至关重要。

在Unity中常用的的图片格式有RGBA32，RGBA16，ETC，PVRTC等。这里我们主要讨论带透明通道的RGBA32和RGBA16这两种格式的图片在Unity占用的内存空间已经优化方案。

我们知道，RGBA32是R,G,B,A四个通道每个通道用8位来表示，RGBA16则是用4位。所以RGBA32能够带来更好的显示效果。同时也会带来更大的内存消耗。  
万事总会存在利弊，这个算法在消除了色阶的同事，带来的是更多的噪点。所以这个方法不适用于图片需要放大来显示的。总体来说，该方案在一定程度上还是能够带来很好的效果。  
最后把算法的核心代码贴出来 。

public class TextureImportSetting : AssetPostprocessor \{

string\[\] assetTexturePath = new string\[\]\{"Assets/Resources/TextureVN/"\}; //放置需要优化的路径  
void OnPreprocessTexture()\{  
foreach (var str in assetTexturePath)  
\{  
if (this.assetPath.StartsWith(str) )  
\{  
TextureImporter textureImporter = this.assetImporter as TextureImporter;  
textureImporter.textureType = TextureImporterType.Advanced;  
textureImporter.npotScale = TextureImporterNPOTScale.ToNearest;  
textureImporter.mipmapEnabled = false;  
textureImporter.isReadable = false;  
if ( textureImporter.DoesSourceTextureHaveAlpha())  
\{  
textureImporter.textureFormat = TextureImporterFormat.RGBA32;  
\}  
\}  
\}  
\}  
public static void OnPostprocessRGB16 (Texture2D texture)  
\{

var texw = texture.width;  
var texh = texture.height;

var pixels = texture.GetPixels ();  
var offs = 0;

var k1Per15 = 1.0f / 15.0f;  
var k1Per16 = 1.0f / 16.0f;  
var k3Per16 = 3.0f / 16.0f;  
var k5Per16 = 5.0f / 16.0f;  
var k7Per16 = 7.0f / 16.0f;

for (var y = 0; y < texh; y++) \{  
for (var x = 0; x < texw; x++) \{  
float a = pixels \[offs\].a;  
float r = pixels \[offs\].r;  
float g = pixels \[offs\].g;  
float b = pixels \[offs\].b;

var a2 = Mathf.Clamp01 (Mathf.Floor (a  *16)*  k1Per15);  
var r2 = Mathf.Clamp01 (Mathf.Floor (r  *16)*  k1Per15);  
var g2 = Mathf.Clamp01 (Mathf.Floor (g  *16)*  k1Per15);  
var b2 = Mathf.Clamp01 (Mathf.Floor (b  *16)*  k1Per15);

var ae = a - a2;  
var re = r - r2;  
var ge = g - g2;  
var be = b - b2;

pixels \[offs\].a = a2;  
pixels \[offs\].r = r2;  
pixels \[offs\].g = g2;  
pixels \[offs\].b = b2;

var n1 = offs + 1;  
var n2 = offs + texw - 1;  
var n3 = offs + texw;  
var n4 = offs + texw + 1;

if (x < texw - 1) \{  
pixels \[n1\].a += ae \* k7Per16;  
pixels \[n1\].r += re \* k7Per16;  
pixels \[n1\].g += ge \* k7Per16;  
pixels \[n1\].b += be \* k7Per16;  
\}

if (y < texh - 1) \{  
pixels \[n3\].a += ae \* k5Per16;  
pixels \[n3\].r += re \* k5Per16;  
pixels \[n3\].g += ge \* k5Per16;  
pixels \[n3\].b += be \* k5Per16;

if (x > 0) \{  
pixels \[n2\].a += ae \* k3Per16;  
pixels \[n2\].r += re \* k3Per16;  
pixels \[n2\].g += ge \* k3Per16;  
pixels \[n2\].b += be \* k3Per16;  
\}

if (x < texw - 1) \{  
pixels \[n4\].a += ae \* k1Per16;  
pixels \[n4\].r += re \* k1Per16;  
pixels \[n4\].g += ge \* k1Per16;  
pixels \[n4\].b += be \* k1Per16;  
\}  
\}

offs++;  
\}  
\}

texture.SetPixels (pixels);  
EditorUtility.CompressTexture (texture, TextureFormat.RGBA4444, TextureCompressionQuality.Best);  
\}  
void OnPostprocessTexture(Texture2D texture)\{

foreach (var str in assetTexturePath)  
\{  
if (this.assetPath.StartsWith(str) )  
\{  
TextureImporter textureImporter = this.assetImporter as TextureImporter;  
if ( textureImporter.DoesSourceTextureHaveAlpha())  
\{  
OnPostprocessRGB16(texture);  
\}  
\}  
\}  
\}  
\}  
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