【UE4 C++】 外部圖片讀取、Texture 保存 png

藍圖版

導入外部圖片

file://E:/UE___Projects_Test/MyProjectAAA/Plugins/WXimage.jpg

導出圖圖片

• 一般導出 .hdr 文件
• 導出 png 設置一些格式

---

C++ 版

讀取外部圖片

• build.cs 添加 ImageWrapper 模塊，使用時注意添加相關頭文件

  PublicDependencyModuleNames.AddRange(new string[] { "Core", "CoreUObject", "Engine", "InputCore", "ImageWrapper" });
  

• 支持圖片類型

  • png
  • jpg
  • bmp
  • ico
  • exr
  • icns

• 注意 jpg 讀取后 R 和 B 的通道位置

  • ERGBFormat::RGBA、PF_R8G8B8A8 → ERGBFormat::BGR、PF_B8G8R8A8

• 代碼實現（4.26）

  UENUM(BlueprintType)
  enum class EImgFormat : uint8
  {
  
  	/** Portable Network Graphics. */
  	PNG = 0,
  
  	/** Joint Photographic Experts Group. */
  	JPEG,
  
  	/** Single channel JPEG. */
  	GrayscaleJPEG,
  
  	/** Windows Bitmap. */
  	BMP,
  
  	/** Windows Icon resource. */
  	ICO,
  
  	/** OpenEXR (HDR) image file format. */
  	EXR,
  
  	/** Mac icon. */
  	ICNS
  };
  
  UTexture2D* ADataDriveActor::ImportImage(const FString& path, EImgFormat Type, bool& IsValid, int32& OutWidth, int32& OutHeight)
  {
  	UTexture2D* Texture = nullptr;
  	IsValid = false;
  	// 文件是否存在
  	if (!FPlatformFileManager::Get().GetPlatformFile().FileExists(*path))
  	{
  		return nullptr;
  	}
  	// 圖片是否加載
  	TArray<uint8> RawFileData;
  	if (!FFileHelper::LoadFileToArray(RawFileData, *path))
  	{
  		return nullptr;
  	}
  
  	IImageWrapperModule& ImageWrapperModule = FModuleManager::LoadModuleChecked<IImageWrapperModule>(FName("ImageWrapper"));
  	// 自定義枚舉轉換 EImageFormat
  	// IImageWrapperPtr 變更為 TSharedPtr<IImageWrapper>
  	TSharedPtr<IImageWrapper> ImageWrapper = ImageWrapperModule.CreateImageWrapper(static_cast<EImageFormat>((int8)Type));
  	
  	if (ImageWrapper.IsValid() && ImageWrapper->SetCompressed(RawFileData.GetData(), RawFileData.Num()))
  	{
  		// 此處有所變動 低版本為 const TArray<uint8>* UncompressedRGBA = nullptr;
  		TArray<uint8> UncompressedRGBA ;
  		if (ImageWrapper->GetRaw(ERGBFormat::RGBA, 8, UncompressedRGBA))
  		{
  			Texture = UTexture2D::CreateTransient(ImageWrapper->GetWidth(), ImageWrapper->GetHeight(), PF_R8G8B8A8);
  			if (Texture != nullptr)
  			{
  				IsValid = true;
  				OutWidth = ImageWrapper->GetWidth();
  				OutHeight = ImageWrapper->GetHeight();
  				void* TextureData = Texture->PlatformData->Mips[0].BulkData.Lock(LOCK_READ_WRITE);
  				FMemory::Memcpy(TextureData, UncompressedRGBA.GetData(), UncompressedRGBA.Num());
  				Texture->PlatformData->Mips[0].BulkData.Unlock();
  				Texture->UpdateResource();
  			}
  		}
  	}
  	return Texture;
  }
  

  

Texture 導出 圖片

• 原博客地址

• 使用 mip.BulkData.Lock(LOCK_READ_WRITE) 前需要對Texture 設置一些參數，否則會返回 nullptr

  • CompressionSettings set to VectorDisplacementmap
  • MipGenSettings to NoMipmaps
  • SRGB to false

• 代碼實現

  bool ADataDriveActor::ExportImage(UTexture2D* Texture2D, const FString& Path)
  {
  	// setup required parameters
  	TextureCompressionSettings OldCompressionSettings = Texture2D->CompressionSettings;
  	TextureMipGenSettings OldMipGenSettings = Texture2D->MipGenSettings;
  	bool OldSRGB = Texture2D->SRGB;
  
  	Texture2D->CompressionSettings = TextureCompressionSettings::TC_VectorDisplacementmap;
  	Texture2D->MipGenSettings = TextureMipGenSettings::TMGS_NoMipmaps;
  	Texture2D->SRGB = false;
  	Texture2D->UpdateResource();
  
  	FTexture2DMipMap& mipmap = Texture2D->PlatformData->Mips[0];
  	uint8* Data = (uint8*)mipmap.BulkData.Lock(LOCK_READ_WRITE);
  	//FColor* FormatedImageData = static_cast<FColor*>(mipmap.BulkData.Lock(LOCK_READ_WRITE));
  	if (Data == nullptr)
  	{
  		mipmap.BulkData.Unlock(); // 不釋放，會卡住
  		Texture2D->UpdateResource();
  		return false;
  	}
  
  	int width = Texture2D->PlatformData->SizeX;
  	int height = Texture2D->PlatformData->SizeY;
  	TArray<FColor> nColors;
  
  	for (int32 y = 0; y < height; y++)
  	{
  		for (int32 x = 0; x < width; x++)
  		{
  			FColor bColor;
  			bColor.B = Data[(y * width + x) * 4 + 0];//B 0 - 255
  			bColor.G = Data[(y * width + x) * 4 + 1];//G
  			bColor.R = Data[(y * width + x) * 4 + 2];//R
  			bColor.A = Data[(y * width + x) * 4 + 3];//A 
  			nColors.Add(bColor);
  		}
  	}
  	mipmap.BulkData.Unlock();
  
  	// return old parameters
  	Texture2D->CompressionSettings = OldCompressionSettings;
  	Texture2D->MipGenSettings = OldMipGenSettings;
  	Texture2D->SRGB = OldSRGB;
  
  	Texture2D->UpdateResource();
  
  	//獲取 uint8 數據，保存
  	TArray<uint8> ImgData;
  	FImageUtils::CompressImageArray(width, height, nColors, ImgData);
  	return FFileHelper::SaveArrayToFile(ImgData, *Path);
  }