项目中UI经常要用到动态加载图片，比较简单的方法是使用UITexture控件，这样只用3W类下载好图片后直接给UITexture控件赋值就好了，缺点是DrawCall太高了，一个UITexture一个DrawCall，通常只有是背景图片这种才会使用UITexture控件，如果是下拉列表项，我们通常都是使用的UISprite控件，这时就需要我们在程序运行时，由程序创建图集，给UISprite控件使用。
请先看一下帖子：
这帖子的第一种方法其实已经说明了如何在程序中创建图集，只不过他这里是使用一张图片做成图集，再给UISprite控件使用。
==================================================================
public class ImageLoader : MonoBehaviour {
//需要加载动态图片的对象
public UISprite m_img;
//自用的Atlas
private UIAtlas m_uiAtlas;
///
/// 加载的贴图
///
/// Tex.
public void ImageLoad(Texture2D tex)
{
if(tex == null)
{
return;
}
if(tex.name == m_img.spriteName)
{
return;
}
//准备对象和材质球
if(m_uiAtlas == null)
{
Material mat;
Shader shader = Shader.Find(“Unlit/Transparent Colored”);
mat = new Material(shader);
m_uiAtlas = this.gameObject.AddComponent();
m_uiAtlas.spriteMaterial = mat;
}
//设定贴图
m_uiAtlas.spriteMaterial.mainTexture = tex;
m_uiAtlas.coordinates = UIAtlas.Coordinates.Pixels;
//为对应UISprite接口，给Atlas加对象
UIAtlas.Sprite sprite = new UIAtlas.Sprite();
sprite.name = tex.name;
sprite.outer = sprite.inner = new Rect(0f, 0f, tex.width, tex.height);
m_uiAtlas.spriteList.Clear();
m_uiAtlas.spriteList.Add(sprite);
//设置完成
m_img.atlas = m_uiAtlas;
m_img.spriteName = tex.name;
}
}
============================================================
我们工作中常常遇到的是需要将多张图片制作成一个图集，再给多个UISprite控件使用，其实看懂了上面的代码运行时如何生成图集，再结合平常在编辑器中制作图集，答案就已经出来了。请大家好好看看NGUI的编辑器脚本UIAtlasMaker，也就是我们平常在编辑器中制作图集时用的脚本。我们缺少的仅仅是将多张图片PackTextures（打包）成一张大图（也就是我们的图集啦），其实UIAtlasMaker脚本那么长，核心的操作也就是为了PackTextures，也就是unity3d的API里Texture2D.PackTextures函数，这里大家可以参考我以前转的别人的一篇关于该函数用法的文章：
和一篇别人分析UIAtlasMaker脚本的文章：
好了，最后就是我将UIAtlasMaker脚本里打包操作的函数拔出来后的工具类了，只有CreatAtlasFromTex这一个对外使用的函数。使用时只需要传人个UIAtlas组件和图片LIST就可以了，图集生成好后，UISprite控件就可以使用该动态图集了，这样好多个UISprite控件组成的下拉列表项只占一个DrawCall。
=============================CreatAtlas.cs=============================
using UnityEngine;
using System.Collections.Generic;
///
/// 运行时创建NGUI图集，NGUI2.6.3
///
public static class CreatAtlas {
class SpriteEntry {
public Texture2D tex; // Sprite texture -- original texture or a temporary texture
public Rect rect; // Sprite\'s outer rectangle within the generated texture atlas
public int minX = 0; // Padding, if any (set if the sprite is trimmed)
public int maxX = 0;
public int minY = 0;
public int maxY = 0;
public bool temporaryTexture = false; // Whether the texture is temporary and should be deleted
}
static Shader s_shader = Shader.Find("Unlit/Transparent Colored");
static Material s_mat = new Material(s_shader);
static int s_maximumAtlasSize = 2048;
static TextureFormat s_TextureFormat = TextureFormat.RGBA32;
static void Init ( UIAtlas uIAtlas ) {
if ( uIAtlas.spriteMaterial == null ) {
// 准备材质球
uIAtlas.spriteMaterial = s_mat;
}
}
///
/// 运行时创建NGUI图集，NGUI2.6.3
///
/// 使用该UIAtlas在运行时创建NGUI图集
/// 用雨创建图集的多张小图
public static void CreatAtlasFromTex ( UIAtlas uIAtlas, List textures ) {
if ( null == textures || textures.Count <= 0 ) {
Debug.LogWarning("textures is null or count <= 0 !!");
return;
}
if ( null == uIAtlas ) {
Debug.LogWarning("uIAtlas is null");
return;
} else {
Init(uIAtlas);
// 设定贴图，将小图映射为SpriteEntry
List sprites = CreateSprites(textures);
// 将多个小图PackTexture为一张大图，给图集用
uIAtlas.spriteMaterial.mainTexture = UpdateTexture(uIAtlas, sprites);
ReplaceSprites(uIAtlas, sprites);
}
}
#region copy UIAtlasMaker编辑器脚本
static List CreateSprites (List textures) {
List list = new List( );
foreach (Texture tex in textures) {
Texture2D oldTex = tex as Texture2D;
if (oldTex == null) continue;
// If we want to trim transparent pixels, there is more work to be done
Color32[ ] pixels = oldTex.GetPixels32( );
int xmin = oldTex.width;
int xmax = 0;
int ymin = oldTex.height;
int ymax = 0;
int oldWidth = oldTex.width;
int oldHeight = oldTex.height;
// Find solid pixels
for (int y = 0, yw = oldHeight; y < yw; ++y) {
for (int x = 0, xw = oldWidth; x < xw; ++x) {
Color32 c = pixels[y * xw + x];
if (c.a != 0) {
if (y < ymin) ymin = y;
if (y > ymax) ymax = y;
if (x < xmin) xmin = x;
if (x > xmax) xmax = x;
}
}
}
int newWidth = (xmax - xmin) + 1;
int newHeight = (ymax - ymin) + 1;
// If the sprite is empty, don\'t do anything with it
if (newWidth > 0 && newHeight > 0) {
SpriteEntry sprite = new SpriteEntry( );
sprite.rect = new Rect(0f, 0f, oldTex.width, oldTex.height);
// If the dimensions match, then nothing was actually trimmed
if (newWidth == oldWidth && newHeight == oldHeight) {
sprite.tex = oldTex;
sprite.temporaryTexture = false;
} else {
// Copy the non-trimmed texture data into a temporary buffer
Color32[ ] newPixels = new Color32[newWidth * newHeight];
for (int y = 0; y < newHeight; ++y) {
for (int x = 0; x < newWidth; ++x) {
int newIndex = y * newWidth + x;
int oldIndex = (ymin + y) * oldWidth + (xmin + x);
newPixels[newIndex] = pixels[oldIndex];
}
}
// Create a new texture
sprite.temporaryTexture = true;
sprite.tex = new Texture2D(newWidth, newHeight);
sprite.tex.name = oldTex.name;
sprite.tex.SetPixels32(newPixels);
sprite.tex.Apply( );
// Remember the padding offset
sprite.minX = xmin;
sprite.maxX = oldWidth - newWidth - xmin;
sprite.minY = ymin;
sprite.maxY = oldHeight - newHeight - ymin;
}
list.Add(sprite);
}
}
return list;
}
static Texture2D UpdateTexture (UIAtlas atlas, List sprites) {
Texture2D tex = new Texture2D(1, 1, s_TextureFormat, false);
PackTextures(tex, sprites);
atlas.spriteMaterial.mainTexture = tex;
return tex;
}
static void PackTextures (Texture2D tex, List sprites) {
Texture2D[ ] textures = new Texture2D[sprites.Count];
for (int i = 0; i < sprites.Count; ++i) textures = sprites.tex;
Rect[ ] rects = tex.PackTextures(textures, 1, s_maximumAtlasSize);
for (int i = 0; i < sprites.Count; ++i) {
sprites.rect = NGUIMath.ConvertToPixels(rects, tex.width, tex.height, true);
}
}
static void ReplaceSprites (UIAtlas atlas, List sprites) {
// Get the list of sprites we\'ll be updating
List spriteList = atlas.spriteList;
List kept = new List( );
// The atlas must be in pixels
atlas.coordinates = UIAtlas.Coordinates.Pixels;
// Run through all the textures we added and add them as sprites to the atlas
for (int i = 0; i < sprites.Count; ++i) {
SpriteEntry se = sprites;
UIAtlas.Sprite sprite = AddSprite(spriteList, se);
kept.Add(sprite);
}
// Remove unused sprites
for (int i = spriteList.Count; i > 0; ) {
UIAtlas.Sprite sp = spriteList[--i];
if (!kept.Contains(sp)) spriteList.RemoveAt(i);
}
atlas.MarkAsDirty( );
}
static UIAtlas.Sprite AddSprite (List sprites, SpriteEntry se) {
UIAtlas.Sprite sprite = null;
// See if this sprite already exists
foreach (UIAtlas.Sprite sp in sprites) {
if (sp.name == se.tex.name) {
sprite = sp;
break;
}
}
if (sprite != null) {
float x0 = sprite.inner.xMin - sprite.outer.xMin;
float y0 = sprite.inner.yMin - sprite.outer.yMin;
float x1 = sprite.outer.xMax - sprite.inner.xMax;
float y1 = sprite.outer.yMax - sprite.inner.yMax;
sprite.outer = se.rect;
sprite.inner = se.rect;
sprite.inner.xMin = Mathf.Max(sprite.inner.xMin + x0, sprite.outer.xMin);
sprite.inner.yMin = Mathf.Max(sprite.inner.yMin + y0, sprite.outer.yMin);
sprite.inner.xMax = Mathf.Min(sprite.inner.xMax - x1, sprite.outer.xMax);
sprite.inner.yMax = Mathf.Min(sprite.inner.yMax - y1, sprite.outer.yMax);
} else {
sprite = new UIAtlas.Sprite( );
sprite.name = se.tex.name;
sprite.outer = se.rect;
sprite.inner = se.rect;
sprites.Add(sprite);
}
float width = Mathf.Max(1f, sprite.outer.width);
float height = Mathf.Max(1f, sprite.outer.height);
// Sprite\'s padding values are relative to width and height
sprite.paddingLeft = se.minX / width;
sprite.paddingRight = se.maxX / width;
sprite.paddingTop = se.maxY / height;
sprite.paddingBottom = se.minY / height;
return sprite;
}
#endregion copy UIAtlasMaker编辑器脚本
}