C++ Builder CE TBitmap->Grayscale png file

//---------------------------------------------------------------------------

#ifndef Unit1H
#define Unit1H
//---------------------------------------------------------------------------
#include <System.Classes.hpp>
#include <Vcl.Controls.hpp>
#include <Vcl.StdCtrls.hpp>
#include <Vcl.Forms.hpp>
#include <Vcl.ExtCtrls.hpp>
//---------------------------------------------------------------------------
class TForm1 : public TForm
{
__published:	// IDE で管理されるコンポーネント
	TImage *Image1;
	TButton *Button1;
	void __fastcall Button1Click(TObject *Sender);
private:	// ユーザー宣言
public:		// ユーザー宣言
	__fastcall TForm1(TComponent* Owner);
};
//---------------------------------------------------------------------------
extern PACKAGE TForm1 *Form1;
//---------------------------------------------------------------------------
#endif

//---------------------------------------------------------------------------

#include <vcl.h>
#include <Vcl.Graphics.hpp>
#include <Vcl.Imaging.pngimage.hpp>
#include <System.Classes.hpp>
#include <memory>
#pragma hdrstop

#include "Unit1.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
	: TForm(Owner)
{
}
//---------------------------------------------------------------------------



void LoadGrayscaleFromBuffer(Graphics::TBitmap* bmp, const Byte* rawBuffer, int width, int height) {
	// 1. Initialize sizes and the 256-color grayscale palette
	bmp->PixelFormat = pf8bit;
	bmp->Width = width;
	bmp->Height = height;

	LOGPALETTE* pPal = (LOGPALETTE*)malloc(sizeof(LOGPALETTE) + (sizeof(PALETTEENTRY) * 256));
	pPal->palVersion = 0x0300;
	pPal->palNumEntries = 256;
	for (int i = 0; i < 256; i++) {
		pPal->palPalEntry[i].peRed   = i;
		pPal->palPalEntry[i].peGreen = i;
		pPal->palPalEntry[i].peBlue  = i;
		pPal->palPalEntry[i].peFlags = 0;
	}
	bmp->Palette = CreatePalette(pPal);
    free(pPal);

    // 2. Copy pixels row-by-row to handle automatic 4-byte alignment padding
	for (int y = 0; y < height; y++) {
        // Point to the beginning of row Y in the destination bitmap
		Byte* destRow = (Byte*)bmp->ScanLine[y];

		// Point to the beginning of row Y in your packed source buffer
        const Byte* srcRow = &rawBuffer[y * width];

        // Copy only the exact pixel width data
		memcpy(destRow, srcRow, width);
    }
}

void __fastcall TForm1::Button1Click(TObject *Sender)
{
	int width = 640;
	int height = 480;

	// Simulate an external 8-bit memory buffer (e.g., from a camera API)
	std::unique_ptr<Byte[]> mockBuffer(new Byte[width * height]);

	// Generate a horizontal gradient pattern
	for (int y = 0; y < height; y++) {
		for (int x = 0; x < width; x++) {
			mockBuffer[(y * width) + x] = (Byte)((x * 255) / width);
		}
	}


	Graphics::TBitmap *bmp = new Graphics::TBitmap();
	LoadGrayscaleFromBuffer(bmp, mockBuffer.get(), width, height);

	// Display inside the TImage component
	Image1->Picture->Assign(bmp);
	//Image1->Picture->SaveToFile("sample.dat");
	//std::unique_ptr<TPngImage> png(new TPngImage());
	TPngImage* png = new TPngImage();

	// Assign the bitmap data directly into the PNG object
	png->Assign(bmp);

	// Save the compressed lossless data directly to disk
	png->SaveToFile("sample.png");
}
//---------------------------------------------------------------------------