}

// Read presents one or more IDAT chunks as one continuous stream (minus the
// intermediate chunk headers and footers). If the PNG data looked like:
//
//	... len0 IDAT xxx crc0 len1 IDAT yy crc1 len2 IEND crc2
//
// then this reader presents xxxyy. For well-formed PNG data, the decoder state
// immediately before the first Read call is that d.r is positioned between the

	// The following is an invalid 1x2 grayscale PNG image. The header is OK,
	// but the zlib-compressed IDAT payload contains two bytes "\x02\x00",
	// which is only one row of data (the leading "\x02" is a row filter).
	const (
		ihdr = "\x00\x00\x00\x0dIHDR\x00\x00\x00\x01\x00\x00\x00\x02\x08\x00\x00\x00\x00\xbc\xea\xe9\xfb"
		idat = "\x00\x00\x00\x0eIDAT\x78\x9c\x62\x62\x00\x04\x00\x00\xff\xff\x00\x06\x00\x03\xfa\xd0\x59\xae"

		e.tmp[3*256+i] = c1.A
	}
	e.writeChunk(e.tmp[:3*len(p)], "PLTE")
	if last != -1 {
		e.writeChunk(e.tmp[3*256:3*256+1+last], "tRNS")
	}
}

// An encoder is an io.Writer that satisfies writes by writing PNG IDAT chunks,
// including an 8-byte header and 4-byte CRC checksum per Write call. Such calls
// should be relatively infrequent, since writeIDATs uses a [bufio.Writer].
//

				switch name {
				case "IHDR":
					bitdepth := data[i+8+8]
					if bitdepth != tc.bitdepth {
						t.Errorf("got bitdepth %d, want %d", bitdepth, tc.bitdepth)
					}
				case "IDAT":
					// Uncompress the image data
					r, err := zlib.NewReader(bytes.NewReader(data[i+8 : i+8+int(length)]))
					if err != nil {
						t.Error(err)
						return
					}
					n, err := io.Copy(io.Discard, r)