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UEC++学习（十七）利用SceneCaptureComponent2d进行截图

news 来源：原创 2024/9/20 16:53:29

最近有个需求是需要将场景中的actor进行截图，并且将截图保存成png，png中需要将场景背景忽略掉，只显示特定的actor。

这里是通过SceneCapture2d组件捕捉场景后，将背景的alpha通道设置为0，实现背景透明的功能。

（一）截图成png

（1）在.h文件

	UFUNCTION(BlueprintCallable)UTexture2D* SaveCaptureScene(bool IsSave, class USceneCaptureComponent2D* SceneCapture, const FString& SavePath, int32 NewWidth = 0, int32 NewHeight = 0, int32 CompressionQuality = 100);//保存为pngbool SaveRenderTargetToDisk(UTextureRenderTarget2D* RenderTarget, const FString& FilePath, int32 NewWidth, int32 NewHeight, int32 CompressionQuality);//设置png的sizevoid ResizeImage(const TArray<FColor>& SourceBitmap, int32 SourceWidth, int32 SourceHeight, int32 TargetWidth, int32 TargetHeight, TArray<FColor>& OutBitmap);//将png转为texture2dUTexture2D* LoadTextureFromFile(const FString& FilePath);

（2）在.cpp文件


#include "Engine/TextureRenderTarget2D.h"
#include "Components/SceneCaptureComponent2D.h"
#include "IImageWrapperModule.h"
#include "IImageWrapper.h"
#include "FileHelper.h"
#include "Paths.h"
#include "Engine/Texture2D.h"
#include "Misc/FileHelper.h"
#include "ImageUtils.h" UTexture2D* YourClass::SaveCaptureScene(const UObject* WorldContextObject, bool IsSave, USceneCaptureComponent2D* SceneCapture, const FString& SavePath, int32 NewWidth, int32 NewHeight, int32 CompressionQuality )
{if (!IsSave){SceneCapture->SetVisibility(false);return nullptr;}if (SceneCapture && SceneCapture->TextureTarget){SceneCapture->SetVisibility(true);// 捕捉场景SceneCapture->CaptureScene();// 将 RenderTarget 保存为 PNG 文件if (SaveRenderTargetToDisk(SceneCapture->TextureTarget, *SavePath,NewWidth,NewHeight,CompressionQuality)){// 导入 PNG 为 UTexture2DUTexture2D* CapturedTexture = LoadTextureFromFile(*SavePath);if (CapturedTexture){// 在此处处理导入的纹理，例如将其应用到材质中UE_LOG(LogTemp, Log, TEXT("LYM_Texture imported successfully."));return CapturedTexture;}else{UE_LOG(LogTemp, Error, TEXT("LYM_Failed to import texture."));return nullptr;}}else{UE_LOG(LogTemp, Error, TEXT("LYM_Failed to SavePNG"));return nullptr;}}UE_LOG(LogTemp, Error, TEXT("LYM_SceneCapture or TextureTarget is invalid."));return nullptr;}bool YourClass::SaveRenderTargetToDisk(UTextureRenderTarget2D* RenderTarget, const FString& FilePath, int32 NewWidth, int32 NewHeight, int32 CompressionQuality)
{FTextureRenderTargetResource* RenderTargetResource = RenderTarget->GameThread_GetRenderTargetResource();if (!RenderTargetResource){return false;}// 创建位图TArray<FColor> Bitmap;if (!RenderTargetResource->ReadPixels(Bitmap)){return false;}int32 Width = RenderTarget->SizeX;int32 Height = RenderTarget->SizeY;// 调整图像大小（如果指定了新的宽度和高度）if (NewWidth > 0 && NewHeight > 0){TArray<FColor> ResizedBitmap;//FImageUtils::ImageResize(Width, Height, Bitmap, NewWidth, NewHeight, ResizedBitmap);ResizeImage(Bitmap, Width, Height, NewWidth, NewHeight, ResizedBitmap);Bitmap = MoveTemp(ResizedBitmap);  // 使用调整后的图像Width = NewWidth;Height = NewHeight;}// 处理位图，设置背景透明for (FColor& Pixel : Bitmap){if (Pixel == FColor::Black) // 假设背景是黑色，或者你可以用特定的颜色进行判断{Pixel.A = 0; // 设置 Alpha 通道为 0，透明UE_LOG(LogTemp, Display, TEXT("LYM_ SetColor = 0"));}}// 压缩为 PNGIImageWrapperModule& ImageWrapperModule = FModuleManager::LoadModuleChecked<IImageWrapperModule>(FName("ImageWrapper"));TSharedPtr<IImageWrapper> ImageWrapper = ImageWrapperModule.CreateImageWrapper(EImageFormat::PNG);if (ImageWrapper.IsValid() && ImageWrapper->SetRaw(Bitmap.GetData(), Bitmap.Num() * sizeof(FColor), Width, Height, ERGBFormat::BGRA, 8)){// 设置压缩质量const TArray<uint8, FDefaultAllocator64> PngData = ImageWrapper->GetCompressed(CompressionQuality);if (FFileHelper::SaveArrayToFile(PngData, *FilePath)){return true;}}return false;
}void YourClass::ResizeImage(const TArray<FColor>& SourceBitmap, int32 SourceWidth, int32 SourceHeight, int32 TargetWidth, int32 TargetHeight, TArray<FColor>& OutBitmap)
{//（1）如果需要填充整个png使用这个//OutBitmap.SetNumUninitialized(TargetWidth * TargetHeight);//float XRatio = static_cast<float>(SourceWidth) / TargetWidth;//float YRatio = static_cast<float>(SourceHeight) / TargetHeight;//for (int32 y = 0; y < TargetHeight; ++y)//{//	for (int32 x = 0; x < TargetWidth; ++x)//	{//		int32 SrcX = FMath::Clamp(static_cast<int32>(x * XRatio), 0, SourceWidth - 1);//		int32 SrcY = FMath::Clamp(static_cast<int32>(y * YRatio), 0, SourceHeight - 1);//		OutBitmap[y * TargetWidth + x] = SourceBitmap[SrcY * SourceWidth + SrcX];//	}//}//(2)如果截图需要居中对齐，用这个// 清空目标位图并初始化为透明OutBitmap.SetNumZeroed(TargetWidth * TargetHeight);// 计算宽高比float SourceAspect = static_cast<float>(SourceWidth) / SourceHeight;float TargetAspect = static_cast<float>(TargetWidth) / TargetHeight;int32 NewWidth, NewHeight;if (SourceAspect > TargetAspect){// 宽度受限NewWidth = TargetWidth;NewHeight = static_cast<int32>(TargetWidth / SourceAspect);}else{// 高度受限NewHeight = TargetHeight;NewWidth = static_cast<int32>(TargetHeight * SourceAspect);}// 调整后的图像居中对齐的偏移量int32 OffsetX = (TargetWidth - NewWidth) / 2;int32 OffsetY = (TargetHeight - NewHeight) / 2;// 转换 TArray<FColor> 为 TArray<FLinearColor>TArray<FLinearColor> SourceData;SourceData.SetNum(SourceWidth * SourceHeight);for (int32 i = 0; i < SourceWidth * SourceHeight; ++i){FColor Color = SourceBitmap[i];SourceData[i] = Color.ReinterpretAsLinear();}// 缩放图像TArray<FLinearColor> ResizedData;ResizedData.SetNum(NewWidth * NewHeight);FImageUtils::ImageResize(SourceWidth, SourceHeight, SourceData, NewWidth, NewHeight, ResizedData);// 转换 TArray<FLinearColor> 回 TArray<FColor>TArray<FColor> ResizedBitmap;ResizedBitmap.SetNum(NewWidth * NewHeight);for (int32 i = 0; i < NewWidth * NewHeight; ++i){ResizedBitmap[i] = ResizedData[i].ToFColor(true);}// 将调整后的图像绘制到目标位图中for (int32 Y = 0; Y < NewHeight; Y++){for (int32 X = 0; X < NewWidth; X++){int32 SourceIndex = Y * NewWidth + X;int32 TargetIndex = (Y + OffsetY) * TargetWidth + (X + OffsetX);OutBitmap[TargetIndex] = ResizedBitmap[SourceIndex];}}
}UTexture2D* YourClass::LoadTextureFromFile(const FString& FilePath)
{TArray<uint8> RawFileData;if (!FFileHelper::LoadFileToArray(RawFileData, *FilePath)){return nullptr; // 文件加载失败}IImageWrapperModule& ImageWrapperModule = FModuleManager::LoadModuleChecked<IImageWrapperModule>(FName("ImageWrapper"));EImageFormat ImageFormat = ImageWrapperModule.DetectImageFormat(RawFileData.GetData(), RawFileData.Num());if (ImageFormat == EImageFormat::Invalid){return nullptr; // 图像格式无效}TSharedPtr<IImageWrapper> ImageWrapper = ImageWrapperModule.CreateImageWrapper(ImageFormat);if (ImageWrapper.IsValid() && ImageWrapper->SetCompressed(RawFileData.GetData(), RawFileData.Num())){TArray<uint8> RawData;if (ImageWrapper->GetRaw(ERGBFormat::BGRA, 8, RawData)){// 创建 UTexture2D 并填充它的数据UTexture2D* Texture = UTexture2D::CreateTransient(ImageWrapper->GetWidth(), ImageWrapper->GetHeight(), PF_B8G8R8A8);if (Texture){void* TextureData = Texture->PlatformData->Mips[0].BulkData.Lock(LOCK_READ_WRITE);//锁定和解锁纹理数据以写入图像内容FMemory::Memcpy(TextureData, RawData.GetData(), RawData.Num());Texture->PlatformData->Mips[0].BulkData.Unlock();//更新纹理资源以使更改生效Texture->UpdateResource();return Texture;}}}return nullptr; // 导入失败
}

（3）在蓝图中添加SceneCapture2d组件：首先如果你不需要这个组件一直捕捉的话，需要将它隐藏并且将自动激活关了，不然会很耗性能