UE4 读取本地图片

参考链接:​​https://answers.unrealengine.com/questions/235086/texture-2d-shows-wrong-colors-from-jpeg-on-html5-p.html​​

我这里，不能将图片全放工程之中，需要在外部在加载图片资源，再来使用

1.通过本地图片路径，获取图片，并将其数据转为uint类型的数组

#pragma region 通过本地图片转换成UTexture2D
UTexture2D* AMyProjectGameMode::GetLocalTexture(const FString &_TexPath)
{
  UTexture2D* OutTex=NULL;
  IImageWrapperModule& imageWrapperModule = FModuleManager::LoadModuleChecked<IImageWrapperModule>(FName("ImageWrapper"));
  IImageWrapperPtr imageWrapper = imageWrapperModule.CreateImageWrapper(EImageFormat::PNG);

  TArray<uint8> OutArray;
  if(FFileHelper::LoadFileToArray(OutArray, *_TexPath))
  {
    if (imageWrapper.IsValid()&&
      imageWrapper->SetCompressed(OutArray.GetData(), OutArray.Num()))
    {
      const TArray<uint8>* uncompressedRGBA = NULL;
      if (imageWrapper->GetRaw(ERGBFormat::RGBA, 8, uncompressedRGBA))
      {
        const TArray<FColor> uncompressedFColor=uint8ToFColor(*uncompressedRGBA);
        OutTex=TextureFromImage(
          imageWrapper->GetWidth(),
          imageWrapper->GetHeight(),
          uncompressedFColor,
          true);
      }
    }
  }
  return OutTex;
}
#pragma endregion

2.将uint8数组转为颜色数组

#pragma region 将uint8数组转为颜色数组
TArray<FColor> AMyProjectGameMode::uint8ToFColor(const TArray<uint8> origin)
{
  TArray<FColor> uncompressedFColor;
  uint8 auxOrigin;
  FColor auxDst;

  for (int i = 0; i < origin.Num(); i++) {
    auxOrigin = origin[i];
    auxDst.R = auxOrigin;
    i++;
    auxOrigin = origin[i];
    auxDst.G = auxOrigin;
    i++;
    auxOrigin = origin[i];
    auxDst.B = auxOrigin;
    i++;
    auxOrigin = origin[i];
    auxDst.A = auxOrigin;
    uncompressedFColor.Add(auxDst);
  }

  return  uncompressedFColor;

}
#pragma endregion

3.将颜色数组赋值给Texture

#pragma region 将颜色数组赋值给Texture
UTexture2D* AMyProjectGameMode::TextureFromImage(const int32 SrcWidth, const int32 SrcHeight, const TArray<FColor> &SrcData, const bool UseAlpha) 
{

  // 创建Texture2D纹理
  UTexture2D* MyScreenshot = UTexture2D::CreateTransient(SrcWidth, SrcHeight, PF_B8G8R8A8);

  // 锁住他的数据，以便修改
  uint8* MipData = static_cast<uint8*>(MyScreenshot->PlatformData->Mips[0].BulkData.Lock(LOCK_READ_WRITE));

  // 创建纹理数据
  uint8* DestPtr = NULL;
  const FColor* SrcPtr = NULL;
  for (int32 y = 0; y<SrcHeight; y++)
  {
    DestPtr = &MipData[(SrcHeight - 1 - y) * SrcWidth * sizeof(FColor)];
    SrcPtr = const_cast<FColor*>(&SrcData[(SrcHeight - 1 - y) * SrcWidth]);
    for (int32 x = 0; x<SrcWidth; x++)
    {
      *DestPtr++ = SrcPtr->B;
      *DestPtr++ = SrcPtr->G;
      *DestPtr++ = SrcPtr->R;
      if (UseAlpha)
      {
        *DestPtr++ = SrcPtr->A;
      }
      else
      {
        *DestPtr++ = 0xFF;
      }
      SrcPtr++;
    }
  }

  // 解锁纹理
  MyScreenshot->PlatformData->Mips[0].BulkData.Unlock();
  MyScreenshot->UpdateResource();

  return MyScreenshot;
}
#pragma endregion

4.我这里建图片路径放在工程的相对路径下，调用GetLocalTexture函数，获取Texture2D

void AMyProjectGameMode::BeginPlay()
{
  const FString _FilePath = FPaths::GameDir() + "video_logo.png";
  _UITex = GetLocalTexture(_FilePath);
}

5.注意别忘了，需要添加两个头文件

#include "Runtime/ImageWrapper/Public/Interfaces/IImageWrapper.h"
#include "Runtime/ImageWrapper/Public/Interfaces/IImageWrapperModule.h"

6.运行截图，我这里将获取的图片放在了UI界面上

7.我在读取jpg格式的图片的时候，颜色明显不对，读png的格式的时候，就完全正常，还未去寻找原因