|| readState.readBKGD
void validate(PngFileReadState readState, PngIhdrChunk headerChunk) {	// A PLTE chunk is invalid if no IHDR has been read or if any PLTE,	// IDAT, or IEND chunk has been read.	if (!readState.readIHDR		|| readState.readPLTE		|| readState.readTRNS		|| readState.readBKGD		|| readState.readIDAT		|| readState.readIEND) 	{		SWT.error(SWT.ERROR_INVALID_IMAGE);	} else {		readState.readPLTE = true;	}		super.validate(readState, headerChunk);		// Palettes cannot be included in grayscale images.	if (!headerChunk.getCanHavePalette()) SWT.error(SWT.ERROR_INVALID_IMAGE);		// Palette chunks' data fields must be event multiples	// of 3. Each 3-byte group represents an RGB value.	if (getLength() % 3 != 0) SWT.error(SWT.ERROR_INVALID_IMAGE);			// Palettes cannot have more entries than 2^bitDepth	// where bitDepth is the bit depth of the image given	// in the IHDR chunk.	if (Compatibility.pow2(headerChunk.getBitDepth()) < getPaletteSize()) {		SWT.error(SWT.ERROR_INVALID_IMAGE);	}		// Palettes cannot have more than 256 entries.	if (256 < getPaletteSize()) SWT.error(SWT.ERROR_INVALID_IMAGE);}