Saving atlas texture generated by Sprite Packer to a PNG file

Question

When I go to: Window > 2D > Sprite Packer I can preview atlas textures generated automatically by Sprite Packer. What I would like to do is to save all of them into PNG files so I can look them up outside Unity editor.

I wrote following script that was supposed to do so:

 using UnityEngine;
 using UnityEditor;
 using UnityEditor.Sprites;
 using System.Collections;
 using System.IO;
 
 public class AtlasTextureExporter : MonoBehaviour
 {
 
     [MenuItem("Tools/Atlas Exporter/Export atlases as PNG")]
     static void ExportAtlases()
     {
         string[] atlasNames = Packer.atlasNames;
 
         for (int i = 0; i < atlasNames.Length; i++)
         {
             string atlasName = atlasNames[i];
             Texture2D[] textures = Packer.GetTexturesForAtlas(atlasName);
 
             for (int j = 0; j < textures.Length; j++)
             {
                 Texture2D texture = textures[j];
                 if (!Directory.Exists(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Desktop) + "/Atlases"))
                     Directory.CreateDirectory(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Desktop) + "/Atlases");
                 FileStream fs = new FileStream(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Desktop) + "/Atlases/" + texture.name + ".png", FileMode.Create);
                 BinaryWriter bw = new BinaryWriter(fs);
                 bw.Write(texture.EncodeToPNG());
                 bw.Close();
                 fs.Close();
             }
         }
     }
 }

But I get following error:

ArgumentException: Texture 'SpriteAtlasTexture-myScene-2048x2048-fmt12' is not readable, the texture memory can not be accessed from scripts. You can make the texture readable in the Texture Import Settings. AtlasTextureExporter.ExportAtlases () (at Assets/Root/Editor/AtlasTextureExporter.cs:27)

How can I make an atlas texture readable? If I cannot, how can I save an atlas texture into a PNG file?

Answer 1

Same issue here with the new SpriteAtlas system. I had to copy the texture to a new RenderTexture first then save the copy, solution from here.

I couldn't find a direct way to access the SpriteAtlas texture so I went through the internal method Unity uses to show it in the inspector panel. Obviously not using this for production, but here is how I save a SpriteAtlas to a PNG:

     [MenuItem("Tools/Export atlases as PNG")]
     static void ExportAtlases() {
         string exportPath = Environment.GetFolderPath(Environment.SpecialFolder.Desktop) + "/Atlases";
         foreach (UnityEngine.Object obj in Selection.objects) {
             SpriteAtlas atlas = (SpriteAtlas) obj;
             if (atlas == null) continue;
             Debug.Log("Exporting selected atlas: " + atlas);
             
             // use reflection to run this internal editor method
             // UnityEditor.U2D.SpriteAtlasExtensions.GetPreviewTextures
             // internal static extern Texture2D[] GetPreviewTextures(this SpriteAtlas spriteAtlas);
             Type type = typeof(UnityEditor.U2D.SpriteAtlasExtensions);
             MethodInfo methodInfo = type.GetMethod("GetPreviewTextures", BindingFlags.Static | BindingFlags.NonPublic);
             if (methodInfo == null) {
                 Debug.LogWarning("Failed to get UnityEditor.U2D.SpriteAtlasExtensions");
                 return;
             }
             Texture2D[] textures = (Texture2D[])methodInfo.Invoke(null, new object[] {atlas} );
             if (textures == null) {
                 Debug.LogWarning("Failed to get texture results");
                 continue;
             }
 
             foreach (Texture2D texture in textures) {
                 // these textures in memory are not saveable so copy them to a RenderTexture first
                 Texture2D textureCopy = DuplicateTexture(texture);
                 if (!Directory.Exists(exportPath)) Directory.CreateDirectory(exportPath);
                 string filename = exportPath + "/" + texture.name + ".png";
                 FileStream fs = new FileStream(filename, FileMode.Create);
                 BinaryWriter bw = new BinaryWriter(fs);
                 bw.Write(textureCopy.EncodeToPNG());
                 bw.Close();
                 fs.Close();
                 Debug.Log("Saved texture to " + filename);
             }
         }
     }
     
     private static Texture2D DuplicateTexture(Texture2D source) {
         RenderTexture renderTex = RenderTexture.GetTemporary(
             source.width,
             source.height,
             0,
             RenderTextureFormat.Default,
             RenderTextureReadWrite.Linear);
 
         Graphics.Blit(source, renderTex);
         RenderTexture previous = RenderTexture.active;
         RenderTexture.active = renderTex;
         Texture2D readableText = new Texture2D(source.width, source.height);
         readableText.ReadPixels(new Rect(0, 0, renderTex.width, renderTex.height), 0, 0);
         readableText.Apply();
         RenderTexture.active = previous;
         RenderTexture.ReleaseTemporary(renderTex);
         return readableText;
     }

Answer 2

Answer by idbrii · Jan 08, 2021 at 09:51 PM

You should be able to make it readable by enabling "Read/Write Enabled" in the atlas's Import Settings inspector.

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Saving atlas texture generated by Sprite Packer to a PNG file

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