return FormatError("total sampling factors too large")
	}

	// zigStart and zigEnd are the spectral selection bounds.
	// ah and al are the successive approximation high and low values.
	// The spec calls these values Ss, Se, Ah and Al.
	//
	// For progressive JPEGs, these are the two more-or-less independent
	// aspects of progression. Spectral selection progression is when not
	// all of a block's 64 DCT coefficients are transmitted in one pass.

		if testing.Short() && i < len(digits)-4 {
			break
		}
		for exp := -30; exp <= 30; exp++ {
			for _, sign := range "+-" {
				for bits := 32; bits <= 64; bits += 32 {
					s := fmt.Sprintf("%c%se%d", sign, digits[:i], exp)
					f, err := strconv.ParseFloat(s, bits)
					if err != nil {
						log.Fatal(err)
					}
					next := math.Nextafter
					if bits == 32 {

		height            int
	}{
		// These bytes come from https://golang.org/issues/22304
		//
		// It encodes a 2147483646 × 2147483646 (i.e. 0x7ffffffe × 0x7ffffffe)
		// NRGBA image. The (width × height) per se doesn't overflow an int64, but
		// (width × height × bytesPerPixel) will.
		{
			src: []byte{
				0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a, 0x00, 0x00, 0x00, 0x0d, 0x49, 0x48, 0x44, 0x52,

	sosMarker  = 0xda // Start Of Scan.
	dqtMarker  = 0xdb // Define Quantization Table.
	driMarker  = 0xdd // Define Restart Interval.
	comMarker  = 0xfe // COMment.
	// "APPlication specific" markers aren't part of the JPEG spec per se,
	// but in practice, their use is described at
	// https://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/JPEG.html
	app0Marker  = 0xe0
	app14Marker = 0xee
	app15Marker = 0xef
)

		if !stringCopy {
			panic(&ValueError{"reflect.Copy", sk})
		}
	}
	src.mustBeExported()

	de := dst.typ().Elem()
	if !stringCopy {
		se := src.typ().Elem()
		typesMustMatch("reflect.Copy", toType(de), toType(se))
	}

	var ds, ss unsafeheader.Slice
	if dk == Array {
		ds.Data = dst.ptr
		ds.Len = dst.Len()
		ds.Cap = ds.Len
	} else {