Barebones example of texture math for minimap, just enough boilerplate to describe GetImageCoordsFromWorldLoc

MinimapUserWidget.cpp

#include "MinimapUserWidget.h"
#include "Kismet/GameplayStatics.h"

FVector2D UMinimapUserWidget::GetImageCoordsFromWorldLoc(FVector WorldLoc) const
{
	// Image coordinate system in UMG is:
	// 0,0 ------> +x
	// |
	// |
	// |
	// +y

	// Find the world location of the top left of the mini map
	// MiniMapOffset gets us to the center of the texture while MiniMapOrthoWidth * 0.5f is half the size of the minimap.
	const float HalfMapLength = MiniMapOrthoWidth * 0.5f;
	const FVector2D TextureTopLeftWorld = MiniMapOffset - MiniMapWorldX * HalfMapLength + MiniMapWorldY * HalfMapLength;
	const FVector2D TextureBottomRightWorld = TextureTopLeftWorld + MiniMapWorldX * MiniMapOrthoWidth - MiniMapWorldY * MiniMapOrthoWidth;
	
	// Calculate our ranges for mapping
	const FVector2D InputRangeWorldX = FVector2D(TextureTopLeftWorld.X, TextureBottomRightWorld.X);
	const FVector2D InputRangeWorldY = FVector2D(TextureTopLeftWorld.Y, TextureBottomRightWorld.Y);
	const FVector2D OutputRangePx = FVector2D(0.f, Image_MiniMapTexture->Brush.GetImageSize().X);

	// Construct the final coordinates
	const float PixelsX = FMath::GetMappedRangeValueClamped(InputRangeWorldX, OutputRangePx, WorldLoc.X);
	const float PixelsY = FMath::GetMappedRangeValueClamped(InputRangeWorldY, OutputRangePx, WorldLoc.Y);
	return FVector2D(PixelsX, PixelsY);	
}

MinimapUserWidget.h

#pragma once

#include "CoreMinimal.h"
#include "Blueprint/UserWidget.h"
#include "MinimapUserWidget.generated.h"

/**
 * 
 */
UCLASS()
class YOURGAME_API UMinimapUserWidget : public UUserWidget
{
	GENERATED_BODY()
public:	
	// The texture for the mini map, assumptions are that this image is square and origin is the center of the image
	UPROPERTY(BlueprintReadWrite, meta = (BindWidget))
	UImage* Image_MiniMapTexture;

	// The Ortho Width of the camera that captured the map image 
	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "MiniMap")
	float MiniMapOrthoWidth;

	// The X/Y offset of the camera that captured the map in world space
	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "MiniMap")
	FVector2D MiniMapOffset;

	// When looking at the mini map this vector should point in the direction of +world X 
	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "MiniMap")
	FVector2D MiniMapWorldX;

	// When looking at the mini map this vector should point in the direction of +world Y 
	// Y positive going down the texture
	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "MiniMap")
	FVector2D MiniMapWorldY;

	// Return image coordinates in texture space from a world location 
	// Image coordinate system in UMG is:
	// 0,0 ------> +x
	// |
	// |
	// |
	// +y
	UFUNCTION(BlueprintCallable)
	FVector2D GetImageCoordsFromWorldLoc(FVector WorldLoc) const;
};