libgo: Update to Go 1.0.3.

[pf3gnuchains/gcc-fork.git] / libgo / go / image / jpeg / writer.go

diff --git a/libgo/go/image/jpeg/writer.go b/libgo/go/image/jpeg/writer.go
index 3322c09..099298e 100644 (file)
--- a/libgo/go/image/jpeg/writer.go
+++ b/libgo/go/image/jpeg/writer.go
@@ -56,26 +56,28 @@ const (
        nQuantIndex
 )
 
-// unscaledQuant are the unscaled quantization tables. Each encoder copies and
-// scales the tables according to its quality parameter.
+// unscaledQuant are the unscaled quantization tables in zig-zag order. Each
+// encoder copies and scales the tables according to its quality parameter.
+// The values are derived from section K.1 after converting from natural to
+// zig-zag order.
 var unscaledQuant = [nQuantIndex][blockSize]byte{
        // Luminance.
        {
-               16, 11, 10, 16, 24, 40, 51, 61,
-               12, 12, 14, 19, 26, 58, 60, 55,
-               14, 13, 16, 24, 40, 57, 69, 56,
-               14, 17, 22, 29, 51, 87, 80, 62,
-               18, 22, 37, 56, 68, 109, 103, 77,
-               24, 35, 55, 64, 81, 104, 113, 92,
-               49, 64, 78, 87, 103, 121, 120, 101,
-               72, 92, 95, 98, 112, 100, 103, 99,
+               16, 11, 12, 14, 12, 10, 16, 14,
+               13, 14, 18, 17, 16, 19, 24, 40,
+               26, 24, 22, 22, 24, 49, 35, 37,
+               29, 40, 58, 51, 61, 60, 57, 51,
+               56, 55, 64, 72, 92, 78, 64, 68,
+               87, 69, 55, 56, 80, 109, 81, 87,
+               95, 98, 103, 104, 103, 62, 77, 113,
+               121, 112, 100, 120, 92, 101, 103, 99,
        },
        // Chrominance.
        {
-               17, 18, 24, 47, 99, 99, 99, 99,
-               18, 21, 26, 66, 99, 99, 99, 99,
-               24, 26, 56, 99, 99, 99, 99, 99,
-               47, 66, 99, 99, 99, 99, 99, 99,
+               17, 18, 18, 24, 21, 24, 47, 26,
+               26, 47, 99, 66, 56, 66, 99, 99,
+               99, 99, 99, 99, 99, 99, 99, 99,
+               99, 99, 99, 99, 99, 99, 99, 99,
                99, 99, 99, 99, 99, 99, 99, 99,
                99, 99, 99, 99, 99, 99, 99, 99,
                99, 99, 99, 99, 99, 99, 99, 99,
@@ -222,7 +224,7 @@ type encoder struct {
        buf [16]byte
        // bits and nBits are accumulated bits to write to w.
        bits, nBits uint32
-       // quant is the scaled quantization tables.
+       // quant is the scaled quantization tables, in zig-zag order.
        quant [nQuantIndex][blockSize]byte
 }
 
@@ -301,7 +303,7 @@ func (e *encoder) writeMarkerHeader(marker uint8, markerlen int) {
 
 // writeDQT writes the Define Quantization Table marker.
 func (e *encoder) writeDQT() {
-       markerlen := 2 + int(nQuantIndex)*(1+blockSize)
+       const markerlen = 2 + int(nQuantIndex)*(1+blockSize)
        e.writeMarkerHeader(dqtMarker, markerlen)
        for i := range e.quant {
                e.writeByte(uint8(i))
@@ -311,7 +313,7 @@ func (e *encoder) writeDQT() {
 
 // writeSOF0 writes the Start Of Frame (Baseline) marker.
 func (e *encoder) writeSOF0(size image.Point) {
-       markerlen := 8 + 3*nColorComponent
+       const markerlen = 8 + 3*nColorComponent
        e.writeMarkerHeader(sof0Marker, markerlen)
        e.buf[0] = 8 // 8-bit color.
        e.buf[1] = uint8(size.Y >> 8)
@@ -344,6 +346,7 @@ func (e *encoder) writeDHT() {
 
 // writeBlock writes a block of pixel data using the given quantization table,
 // returning the post-quantized DC value of the DCT-transformed block.
+// b is in natural (not zig-zag) order.
 func (e *encoder) writeBlock(b *block, q quantIndex, prevDC int) int {
        fdct(b)
        // Emit the DC delta.
@@ -351,8 +354,8 @@ func (e *encoder) writeBlock(b *block, q quantIndex, prevDC int) int {
        e.emitHuffRLE(huffIndex(2*q+0), 0, dc-prevDC)
        // Emit the AC components.
        h, runLength := huffIndex(2*q+1), 0
-       for k := 1; k < blockSize; k++ {
-               ac := div(b[unzig[k]], (8 * int(e.quant[q][k])))
+       for zig := 1; zig < blockSize; zig++ {
+               ac := div(b[unzig[zig]], (8 * int(e.quant[q][zig])))
                if ac == 0 {
                        runLength++
                } else {
@@ -433,10 +436,12 @@ func scale(dst *block, src *[4]block) {
 //     - component 1 uses DC table 0 and AC table 0 "\x01\x00",
 //     - component 2 uses DC table 1 and AC table 1 "\x02\x11",
 //     - component 3 uses DC table 1 and AC table 1 "\x03\x11",
-//     - padding "\x00\x00\x00".
+//     - the bytes "\x00\x3f\x00". Section B.2.3 of the spec says that for
+//       sequential DCTs, those bytes (8-bit Ss, 8-bit Se, 4-bit Ah, 4-bit Al)
+//       should be 0x00, 0x3f, 0x00<<4 | 0x00.
 var sosHeader = []byte{
        0xff, 0xda, 0x00, 0x0c, 0x03, 0x01, 0x00, 0x02,
-       0x11, 0x03, 0x11, 0x00, 0x00, 0x00,
+       0x11, 0x03, 0x11, 0x00, 0x3f, 0x00,
 }
 
 // writeSOS writes the StartOfScan marker.
@@ -444,6 +449,7 @@ func (e *encoder) writeSOS(m image.Image) {
        e.write(sosHeader)
        var (
                // Scratch buffers to hold the YCbCr values.
+               // The blocks are in natural (not zig-zag) order.
                yBlock  block
                cbBlock [4]block
                crBlock [4]block