}

			zig, err = d.refineNonZeroes(b, zig, zigEnd, int32(val0), delta)
			if err != nil {
				return err
			}
			if zig > zigEnd {
				return FormatError("too many coefficients")
			}
			if z != 0 {
				b[unzig[zig]] = z
			}
		}
	}
	if d.eobRun > 0 {
		d.eobRun--
		if _, err := d.refineNonZeroes(b, zig, zigEnd, -1, delta); err != nil {
			return err
		}

// natural (not zig-zag) order.
func (e *encoder) writeBlock(b *block, q quantIndex, prevDC int32) int32 {
	fdct(b)
	// Emit the DC delta.
	dc := div(b[0], 8*int32(e.quant[q][0]))
	e.emitHuffRLE(huffIndex(2*q+0), 0, dc-prevDC)
	// Emit the AC components.
	h, runLength := huffIndex(2*q+1), int32(0)
	for zig := 1; zig < blockSize; zig++ {
		ac := div(b[unzig[zig]], 8*int32(e.quant[q][zig]))
		if ac == 0 {

const (
	adobeTransformUnknown = 0
	adobeTransformYCbCr   = 1
	adobeTransformYCbCrK  = 2
)

// unzig maps from the zig-zag ordering to the natural ordering. For example,
// unzig[3] is the column and row of the fourth element in zig-zag order. The
// value is 16, which means first column (16%8 == 0) and third row (16/8 == 2).
var unzig = [blockSize]int{
	0, 1, 8, 16, 9, 2, 3, 10,

				// C compiler may use. (Clang and GCC mostly seem to follow the scheme X.Y.Z,
				// but in https://go.dev/issue/64619 we saw "8.3 [DragonFly]", and who knows
				// what other C compilers like "zig cc" might report?)
				next := fields[i+1]
				if len(next) > 0 && next[0] >= '0' && next[0] <= '9' {
					version = line
					break
				}
			}
		}
		if version != "" {
			break
		}
	}