UE4插件-读取png图片

一、简介

在UE4中有多种类型的插件，适用于不同的场景。既可以放到引擎中还可以放到项目中，放到引擎中的插件可以被所有项目使用，放到项目中的插件只能被当前项目使用。插件的类型可以在【Edit】->【Plugins】->【New Plugin】中查看

二、创建插件

1.创建一个蓝图插件Blueprint Library命名：ReadImageBP，功能：读取图片并且显示在界面上显示出来

UReadImageBPBPLibrary 类中的代码参考网上的示例代码，并且加以修改
ReadImageBPBPLibrary.h

// Copyright Epic Games, Inc. All Rights Reserved.

#pragma once

#include "Kismet/BlueprintFunctionLibrary.h"
#include "ReadImageBPBPLibrary.generated.h"

/*
*	Function library class.
*	Each function in it is expected to be static and represents blueprint node that can be called in any blueprint.
*
*	When declaring function you can define metadata for the node. Key function specifiers will be BlueprintPure and BlueprintCallable.
*	BlueprintPure - means the function does not affect the owning object in any way and thus creates a node without Exec pins.
*	BlueprintCallable - makes a function which can be executed in Blueprints - Thus it has Exec pins.
*	DisplayName - full name of the node, shown when you mouse over the node and in the blueprint drop down menu.
*				Its lets you name the node using characters not allowed in C++ function names.
*	CompactNodeTitle - the word(s) that appear on the node.
*	Keywords -	the list of keywords that helps you to find node when you search for it using Blueprint drop-down menu.
*				Good example is "Print String" node which you can find also by using keyword "log".
*	Category -	the category your node will be under in the Blueprint drop-down menu.
*
*	For more info on custom blueprint nodes visit documentation:
*	https://wiki.unrealengine.com/Custom_Blueprint_Node_Creation
*/
UCLASS()
class UReadImageBPBPLibrary : public UBlueprintFunctionLibrary {
	GENERATED_UCLASS_BODY()

	UFUNCTION(BlueprintCallable, meta = (DisplayName = "Execute Sample function", Keywords = "ReadImageBP sample test testing"), Category = "ReadImageBPTesting")
	static float ReadImageBPSampleFunction(float Param);

	//获取开发工程目录
	UFUNCTION(BlueprintCallable, Category = "Image")
	static FString getProjectDir();

	//获取打包之后的路径
	UFUNCTION(BlueprintCallable, Category = "Image")
	static FString getPakRootDir();


	UFUNCTION(BlueprintCallable, Category = "Image")
	static class UTexture2D* loadTexture2D(const FString path, bool&isValid, int32&outWidth, int32&outHeight);

private:
	static TArray<FColor> uint8ToFColor(const TArray<uint8> origin);
	static class UTexture2D* TextureFromImage(const int32 SrcWidth, const int32 SrcHeight, const TArray<FColor>& SrcData, const bool UseAlpha);
};

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ReadImageBPBPLibrary.cpp

// Copyright Epic Games, Inc. All Rights Reserved.

#include "ReadImageBPBPLibrary.h"
#include "ReadImageBP.h"
#include "Engine/Texture2D.h"
#include "Core\Public\HAL\PlatformFilemanager.h"
#include "IImageWrapper.h"
#include "IImageWrapperModule.h"

UReadImageBPBPLibrary::UReadImageBPBPLibrary(const FObjectInitializer& ObjectInitializer)
	: Super(ObjectInitializer) {

}

float UReadImageBPBPLibrary::ReadImageBPSampleFunction(float Param) {
	return Param;
}

FString UReadImageBPBPLibrary::getProjectDir() {
	FString dirPath = FPaths::ConvertRelativePathToFull(FPaths::ProjectDir());
	return dirPath;
}

FString UReadImageBPBPLibrary::getPakRootDir() {
	FString dirPath = FPaths::ConvertRelativePathToFull(FPaths::RootDir());
	return dirPath;
}

#pragma region TEXT("通过本地图片转换成UTexture2D")
UTexture2D* UReadImageBPBPLibrary::loadTexture2D(const FString path, bool& isValid, int32& outWidth, int32& outHeight) {
	UTexture2D* texture2D = nullptr;
	IImageWrapperModule& imageWrapperModule = FModuleManager::LoadModuleChecked<IImageWrapperModule>(FName("ImageWrapper"));
	IImageWrapperPtr imageWrapper = imageWrapperModule.CreateImageWrapper(EImageFormat::PNG);

	TArray<uint8> OutArray;
	if (FFileHelper::LoadFileToArray(OutArray, *path)) {
		if (imageWrapper.IsValid() &&
			imageWrapper->SetCompressed(OutArray.GetData(), OutArray.Num())) {
			TArray<uint8> uncompressedRGBA;
			if (imageWrapper->GetRaw(ERGBFormat::RGBA, 8, uncompressedRGBA)) {
				const TArray<FColor> uncompressedFColor = uint8ToFColor(uncompressedRGBA);
				outWidth = imageWrapper->GetWidth();
				outHeight = imageWrapper->GetHeight();
				texture2D = TextureFromImage(imageWrapper->GetWidth(), imageWrapper->GetHeight(), uncompressedFColor, true);
			}
		}
	}
	return texture2D;
}
#pragma endregion

#pragma region TEXT("将uint8数组转为颜色数组")
TArray<FColor> UReadImageBPBPLibrary::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

#pragma region TEXT("将颜色数组赋值给Texture")
UTexture2D* UReadImageBPBPLibrary::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
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修改ReadImageBP.uplugin文件

{
	"FileVersion": 3,
	"Version": 1,
	"VersionName": "1.0",
	"FriendlyName": "ReadImageBP",
	"Description": "",
	"Category": "AAA",
	"CreatedBy": "",
	"CreatedByURL": "",
	"DocsURL": "",
	"MarketplaceURL": "",
	"SupportURL": "",
	"CanContainContent": true,
	"IsBetaVersion": false,
	"IsExperimentalVersion": false,
	"Installed": false,
	"Modules": [
		{
			"Name": "ReadImageBP",
			"Type": "Runtime",
			"LoadingPhase": "PreLoadingScreen",
			"WhitelistPlatforms": [
				"Win64"
			]
		}
	]
}
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2. 图片
   在Pingins下面新建一个文件夹Image,并且在里面添加一直图片
   

3. 使用插件功能
   在对应的插件文件夹下面,新建一个空的Actor,只有一个Box(触发盒子)，新建一个UserWidget,在上面添加一个Image控件，当小白人走进Box的时候，就会调用插件中的函数加载图片，并且在HUD中的Image控件中显示出来
   
   BP_TestReadImage
   
   游戏一启动就把HUD添加到注游戏界面上
   
   当游戏角色进入到触发盒子的时候，就会加载图片并且在Image控件上显示出来，图片路径写固定值/Iamge/2.png
   
   
   运行结果：
   
   aaa