assertEquals(numColorComponents, filter.getColors());
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] data = RawPNGTestUtil.buildGRGBAData(gray, red, green, blue, alpha);
ByteArrayInputStream bais = new ByteArrayInputStream(data);
when(irpng.createInputStream()).thenReturn(bais);
irpnga.outputContents(baos);
if (alpha > -1) {
byte[] expected = RawPNGTestUtil.buildGRGBAData(gray, red, green, blue, -1);
assertArrayEquals(expected, baos.toByteArray());
} else {