Method GenMipMapRGBA

samples/hellovr_vulkan/hellovr_vulkan_main.cpp:2277–2327

----------------------------------------------------------------------------- Purpose: generate next level mipmap for an RGBA image -----------------------------------------------------------------------------

// Purpose: generate next level mipmap for an RGBA image
//-----------------------------------------------------------------------------
void CMainApplication::GenMipMapRGBA( const uint8_t *pSrc, uint8_t *pDst, int nSrcWidth, int nSrcHeight, int *pDstWidthOut, int *pDstHeightOut )
{
	*pDstWidthOut = nSrcWidth / 2;
	if ( *pDstWidthOut <= 0 )
	{
		*pDstWidthOut = 1;
	}
	*pDstHeightOut = nSrcHeight / 2;
	if ( *pDstHeightOut <= 0 )
	{
		*pDstHeightOut = 1;
	}

	for ( int y = 0; y < *pDstHeightOut; y++ )
	{
		for ( int x = 0; x < *pDstWidthOut; x++ )
		{
			int nSrcIndex[4];
			float r = 0.0f;
			float g = 0.0f;
			float b = 0.0f;
			float a = 0.0f;

			nSrcIndex[0] = ( ( ( y * 2 ) * nSrcWidth ) + ( x * 2 ) ) * 4;
			nSrcIndex[1] = ( ( ( y * 2 ) * nSrcWidth ) + ( x * 2 + 1 ) ) * 4;
			nSrcIndex[2] = ( ( ( ( y * 2 ) + 1 ) * nSrcWidth ) + ( x * 2 ) ) * 4;
			nSrcIndex[3] = ( ( ( ( y * 2 ) + 1 ) * nSrcWidth ) + ( x * 2 + 1 ) ) * 4;

			// Sum all pixels
			for ( int nSample = 0; nSample < 4; nSample++ )
			{
				r += pSrc[ nSrcIndex[ nSample ] ];
				g += pSrc[ nSrcIndex[ nSample ] + 1 ];
				b += pSrc[ nSrcIndex[ nSample ] + 2 ];
				a += pSrc[ nSrcIndex[ nSample ] + 3 ];
			}

			// Average results
			r /= 4.0;
			g /= 4.0;
			b /= 4.0;
			a /= 4.0;

			// Store resulting pixels
			pDst[ ( y * ( *pDstWidthOut ) + x ) * 4 ] = ( uint8_t ) ( r );
			pDst[ ( y * ( *pDstWidthOut ) + x ) * 4 + 1] = ( uint8_t ) ( g );
			pDst[ ( y * ( *pDstWidthOut ) + x ) * 4 + 2] = ( uint8_t ) ( b );
			pDst[ ( y * ( *pDstWidthOut ) + x ) * 4 + 3] = ( uint8_t ) ( a );
		}
	}
}

//-----------------------------------------------------------------------------
// Purpose: create a sea of cubes