How do I modify a UTexture2D in a package?

Development Programming & Scripting C++
1

Hi,

I already load a texture form asset and I set it to a material instance. It works fine.

next, I changed the texture data and already called tex->UpdateResource(),

And I can see the change in the editor.

now, I have a problem about how to save it to the origin asset?

I tried a lot of ways, but it didn’t work.

It is strange that if I save it to a new asset(UPackage), there will be no problem.download

origin texture:
1.jpg

after changed:
2.jpg

restart editor:
2c328396bc8192fd0f582209b37ebdd4c7712e75.jpeg

2

the texture in the asset cannot be change by C++ Code?

3

here is the code:



	//	back.uasset it is a texture
	FString Path = TEXT("/Game/back");
	//	load it
	UTexture2D* tmpTex = Cast<UTexture2D>(StaticLoadObject(UTexture2D::StaticClass(), NULL, *Path));
	//	changne all Pixels to RED
	int32 Row = tmpTex->GetSizeY();
	int32 Coloum = tmpTex->GetSizeX();
	FColor* MipData = static_cast<FColor*>(tmpTex->PlatformData->Mips[0].BulkData.Lock(LOCK_READ_WRITE));

	for (int32 RowNum = 0; RowNum < Row; ++RowNum)
	{
		for (int32 ColNum = 0; ColNum < Coloum; ++ColNum)
		{
			FColor& CurColor = MipData(ColNum + (RowNum * Coloum))];
			//	change color
			CurColor = FColor(255, 0, 0, 255);
		}
	}

	tmpTex->PlatformData->Mips[0].BulkData.Unlock();

	//	update data
	tmpTex->UpdateResource();
	tmpTex->MarkPackageDirty();
	UPackage* tmpPkg = Cast<UPackage>(tmpTex->GetOuter());

	if (tmpPkg)
	{
	
		//	save package, now I can see "back.uasset" color is changed.
		//	BUT!!! it's not work. if I restart UE editor, the change is not save, why?

		UPackage::SavePackage(tmpPkg, tmpTex, tmpTex->GetFlags(), *tmpPkg->GetPathName());
	}
4

anyone can offer me aid?

5

the texture your loaded is considered as have been saved by the ue, so you should reset the sign to unsaved .eg
Result->MarkPackageDirty();

7

Hello, I’m having a similar issue and marking the package as dirty doesn’t solve the problem : I try to save a texture procedurally generated, but when I re-open the editor, the texture asset is here but the texture is black. It’s like the changes to the texture PlatformData have not been saved. Have you solved this?

8

Have you checked that the class you’re using isn’t Transient? I.e, dumps all it’s data when being saved?

Render Targets are probably Transient, for example.

9

I don’t think it is transient, I’m trying to save a UTexture2D created by NewObject<UTexture2D>. It appears well in the editor after being generated (so I think it is, at least, partly saved), but it disappears when the editor is being reloaded.
I’ve posted details and code on AnswerHub https://answers.unrealengine.com/que…d-texture.html

10

I’m still looking at it and I may have found something: it seems that the PlatformData (FTexturePlatformData*) where I store the data of the UTexture2D is not saved (it explains why the dimensions appear as 0x0 and why the PixelFormat is “unknown” at loading -> I store this data in the PlatformData field). Could it be possible that it is transient? If so, is there a field of UTexture2D which is supposed to persistently store the data so that we can procedurally edit a texture and save the result?

11

Finally, I’ve found the answer: indeed PlatformData is not saved with UPackage::SavePackage. I had use UTexture::Source.Init() to initialize data in the texture that can be persisted.
So, the line I’ve added (before the call to UpdateResource) is:

NewTexture->Source.Init(TextureWidth, TextureHeight, 1, 1, ETextureSourceFormat::TSF_BGRA8, Pixels);

I give more details in the attached link.

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