Reading texture from texture atlas by name or path

Question

I need to create a texture Atlas dynamically, so I have used Texture2D.PackTextures to pack all textures in a folder named "Images" in my Resources folder.

 Texture2D[] atlasTextures = Resources.LoadAll<Texture2D>("Images");
 
             Texture2D atlas = new Texture2D(4096, 4096);
             Rect[] rects = atlas.PackTextures(atlasTextures, 2, 4096);
 
             string atlasDirPath = Application.persistentDataPath + "/Resources/Images";
             if (!Directory.Exists(atlasDirPath))
             {
                 Directory.CreateDirectory(atlasDirPath);
             }
             FileStream fs = new FileStream(atlasDirPath+"Atlas.png", FileMode.Create);
             BinaryWriter bw = new BinaryWriter(fs);
             bw.Write(atlas.EncodeToPNG());
             bw.Close();
             fs.Close();

So an Atlas Images is perfectly generated and saved in the persistent path. Now, I need to get a particluar texture individually and convert it to sprite and add it to spriteRenderer in my scene. But to select a texture, I only have the name/path of the texture. But Texture2D.PackTextures returns Rect[] array. Now I don't understand how should I pick a particular texture from the atlas with me only having the name of the texture.

Answer 1

In theory, the rect array returned from the packing function should match the order of the input textures - as such, if you were to also cache the source textures (or at least some of their data) you would be able to use that and match the textures up with their positions;

 Dictionary<string, Rect> m_AtlasTextures = new Dictionary<string, Rect>();
 
 ...
 
 Texture2D[] atlasTextures = Resources.LoadAll<Texture2D>("Images");
 
 Texture2D atlas = new Texture2D(4096, 4096);
 Rect[] rects = atlas.PackTextures (atlasTextures, 2, 4096);
 
 for (int i = 0; i < atlasTextures.Length; i++)
 {
     // Cache each texture rect by its corresponding texture name
     m_AtlasTextures[atlasTextures[i].name] = rects[i];
 }
 
 ...
 
 // Then, you can fetch the texture coordinates like so
 public Rect GetAtlasTextureCoordsByName (string a_TextureName)
 {
     return m_AtlasTextures[a_TextureName];
 }

I have not tested this, but I can't imagine the rect array not matching the order of the input textures, otherwise the data would be useless - there would be no way of knowing what element a rect would be pointing to.

Reading texture from texture atlas by name or path

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