Imaging's low level interface is set of functions operating on TImageData structure and TDynImageDataArray. These functions are implemented in Imaging.pas unit and you can find how to use them in How To ... section. You can also look at Demos section. Low level interface is accessible from programming languages other than Object Pascal. Information on this can be found in Using dll/so Access section. There are more functions in Imaging that are not part of low level interface but can be freely used with it. Ulike those, low level interface functions are provided for other programming languages too. Look at Imaging.pas, ImagingFormats.pas, and other units for more functions. Here is the table with all low level interface functions currently available.

General Functions	InitImage	NewImage	TestImage	FreeImage	FreeImagesInArray	TestImagesInArray	DetermineFileFormat	DetermineStreamFormat	DetermineMemoryFormat	IsFileFormatSupported	EnumFileFormats	Loading Functions	LoadImageFromFile	LoadImageFromStream	LoadImageFromMemory	LoadMultiImageFromFile	LoadMultiImageFromStream	LoadMultiImageFromMemory	Saving Functions	SaveImageToFile	SaveImageToStream	SaveImageToMemory	SaveMultiImageToFile	SaveMultiImageToStream	SaveMultiImageToMemory	Manipulation Functions	CloneImage	ConvertImage	FlipImage	MirrorImage	ResizeImage	SwapChannels	ReduceColors	GenerateMipMaps	MapImageToPalette	SplitImage	MakePaletteForImages	RotateImage	Drawing/Pixel Functions	CopyRect	FillRect	ReplaceColor	StretchRect	GetPixelDirect	SetPixelDirect	GetPixel32	SetPixel32	GetPixelFP	SetPixelFP	Palette Functions	NewPalette	FreePalette	CopyPalette	FindColor	FillGrayscalePalette	FillCustomPalette	SwapChannelsOfPalette	Options Functions	SetOption	GetOption	PushOptions	PopOptions	Image Format Functions	GetImageFormatInfo	GetPixelsSize	IO Functions	SetUserFileIO	ResetFileIO

You can find other functions in Reference but they are not available for other languages thus they are not part of the low level interface. Some of them are even dangerous to use if you do not know what you are doing.