mirror of
https://github.com/superseriousbusiness/gotosocial.git
synced 2024-12-05 18:12:46 +00:00
94e87610c4
* add back exif-terminator and use only for jpeg,png,webp * fix arguments passed to terminateExif() * pull in latest exif-terminator * fix test * update processed img --------- Co-authored-by: tobi <tobi.smethurst@protonmail.com>
320 lines
10 KiB
Go
320 lines
10 KiB
Go
// Copyright 2017 Google Inc. All rights reserved.
|
|
//
|
|
// Licensed under the Apache License, Version 2.0 (the "License");
|
|
// you may not use this file except in compliance with the License.
|
|
// You may obtain a copy of the License at
|
|
//
|
|
// http://www.apache.org/licenses/LICENSE-2.0
|
|
//
|
|
// Unless required by applicable law or agreed to in writing, software
|
|
// distributed under the License is distributed on an "AS IS" BASIS,
|
|
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
// See the License for the specific language governing permissions and
|
|
// limitations under the License.
|
|
|
|
package s2
|
|
|
|
import (
|
|
"errors"
|
|
"fmt"
|
|
|
|
"github.com/golang/geo/r3"
|
|
)
|
|
|
|
// maxEncodedVertices is the maximum number of vertices, in a row, to be encoded or decoded.
|
|
// On decode, this defends against malicious encodings that try and have us exceed RAM.
|
|
const maxEncodedVertices = 50000000
|
|
|
|
// xyzFaceSiTi represents the The XYZ and face,si,ti coordinates of a Point
|
|
// and, if this point is equal to the center of a Cell, the level of this cell
|
|
// (-1 otherwise). This is used for Loops and Polygons to store data in a more
|
|
// compressed format.
|
|
type xyzFaceSiTi struct {
|
|
xyz Point
|
|
face int
|
|
si, ti uint32
|
|
level int
|
|
}
|
|
|
|
const derivativeEncodingOrder = 2
|
|
|
|
func appendFace(faces []faceRun, face int) []faceRun {
|
|
if len(faces) == 0 || faces[len(faces)-1].face != face {
|
|
return append(faces, faceRun{face, 1})
|
|
}
|
|
faces[len(faces)-1].count++
|
|
return faces
|
|
}
|
|
|
|
// encodePointsCompressed uses an optimized compressed format to encode the given values.
|
|
func encodePointsCompressed(e *encoder, vertices []xyzFaceSiTi, level int) {
|
|
var faces []faceRun
|
|
for _, v := range vertices {
|
|
faces = appendFace(faces, v.face)
|
|
}
|
|
encodeFaces(e, faces)
|
|
|
|
type piQi struct {
|
|
pi, qi uint32
|
|
}
|
|
verticesPiQi := make([]piQi, len(vertices))
|
|
for i, v := range vertices {
|
|
verticesPiQi[i] = piQi{siTitoPiQi(v.si, level), siTitoPiQi(v.ti, level)}
|
|
}
|
|
piCoder, qiCoder := newNthDerivativeCoder(derivativeEncodingOrder), newNthDerivativeCoder(derivativeEncodingOrder)
|
|
for i, v := range verticesPiQi {
|
|
f := encodePointCompressed
|
|
if i == 0 {
|
|
// The first point will be just the (pi, qi) coordinates
|
|
// of the Point. NthDerivativeCoder will not save anything
|
|
// in that case, so we encode in fixed format rather than varint
|
|
// to avoid the varint overhead.
|
|
f = encodeFirstPointFixedLength
|
|
}
|
|
f(e, v.pi, v.qi, level, piCoder, qiCoder)
|
|
}
|
|
|
|
var offCenter []int
|
|
for i, v := range vertices {
|
|
if v.level != level {
|
|
offCenter = append(offCenter, i)
|
|
}
|
|
}
|
|
e.writeUvarint(uint64(len(offCenter)))
|
|
for _, idx := range offCenter {
|
|
e.writeUvarint(uint64(idx))
|
|
e.writeFloat64(vertices[idx].xyz.X)
|
|
e.writeFloat64(vertices[idx].xyz.Y)
|
|
e.writeFloat64(vertices[idx].xyz.Z)
|
|
}
|
|
}
|
|
|
|
func encodeFirstPointFixedLength(e *encoder, pi, qi uint32, level int, piCoder, qiCoder *nthDerivativeCoder) {
|
|
// Do not ZigZagEncode the first point, since it cannot be negative.
|
|
codedPi, codedQi := piCoder.encode(int32(pi)), qiCoder.encode(int32(qi))
|
|
// Interleave to reduce overhead from two partial bytes to one.
|
|
interleaved := interleaveUint32(uint32(codedPi), uint32(codedQi))
|
|
|
|
// Write as little endian.
|
|
bytesRequired := (level + 7) / 8 * 2
|
|
for i := 0; i < bytesRequired; i++ {
|
|
e.writeUint8(uint8(interleaved))
|
|
interleaved >>= 8
|
|
}
|
|
}
|
|
|
|
// encodePointCompressed encodes points into e.
|
|
// Given a sequence of Points assumed to be the center of level-k cells,
|
|
// compresses it into a stream using the following method:
|
|
// - decompose the points into (face, si, ti) tuples.
|
|
// - run-length encode the faces, combining face number and count into a
|
|
// varint32. See the faceRun struct.
|
|
// - right shift the (si, ti) to remove the part that's constant for all cells
|
|
// of level-k. The result is called the (pi, qi) space.
|
|
// - 2nd derivative encode the pi and qi sequences (linear prediction)
|
|
// - zig-zag encode all derivative values but the first, which cannot be
|
|
// negative
|
|
// - interleave the zig-zag encoded values
|
|
// - encode the first interleaved value in a fixed length encoding
|
|
// (varint would make this value larger)
|
|
// - encode the remaining interleaved values as varint64s, as the
|
|
// derivative encoding should make the values small.
|
|
// In addition, provides a lossless method to compress a sequence of points even
|
|
// if some points are not the center of level-k cells. These points are stored
|
|
// exactly, using 3 double precision values, after the above encoded string,
|
|
// together with their index in the sequence (this leads to some redundancy - it
|
|
// is expected that only a small fraction of the points are not cell centers).
|
|
//
|
|
// To encode leaf cells, this requires 8 bytes for the first vertex plus
|
|
// an average of 3.8 bytes for each additional vertex, when computed on
|
|
// Google's geographic repository.
|
|
func encodePointCompressed(e *encoder, pi, qi uint32, level int, piCoder, qiCoder *nthDerivativeCoder) {
|
|
// ZigZagEncode, as varint requires the maximum number of bytes for
|
|
// negative numbers.
|
|
zzPi := zigzagEncode(piCoder.encode(int32(pi)))
|
|
zzQi := zigzagEncode(qiCoder.encode(int32(qi)))
|
|
// Interleave to reduce overhead from two partial bytes to one.
|
|
interleaved := interleaveUint32(zzPi, zzQi)
|
|
e.writeUvarint(interleaved)
|
|
}
|
|
|
|
type faceRun struct {
|
|
face, count int
|
|
}
|
|
|
|
func decodeFaceRun(d *decoder) faceRun {
|
|
faceAndCount := d.readUvarint()
|
|
ret := faceRun{
|
|
face: int(faceAndCount % numFaces),
|
|
count: int(faceAndCount / numFaces),
|
|
}
|
|
if ret.count <= 0 && d.err == nil {
|
|
d.err = errors.New("non-positive count for face run")
|
|
}
|
|
return ret
|
|
}
|
|
|
|
func decodeFaces(numVertices int, d *decoder) []faceRun {
|
|
var frs []faceRun
|
|
for nparsed := 0; nparsed < numVertices; {
|
|
fr := decodeFaceRun(d)
|
|
if d.err != nil {
|
|
return nil
|
|
}
|
|
frs = append(frs, fr)
|
|
nparsed += fr.count
|
|
}
|
|
return frs
|
|
}
|
|
|
|
// encodeFaceRun encodes each faceRun as a varint64 with value numFaces * count + face.
|
|
func encodeFaceRun(e *encoder, fr faceRun) {
|
|
// It isn't necessary to encode the number of faces left for the last run,
|
|
// but since this would only help if there were more than 21 faces, it will
|
|
// be a small overall savings, much smaller than the bound encoding.
|
|
coded := numFaces*uint64(fr.count) + uint64(fr.face)
|
|
e.writeUvarint(coded)
|
|
}
|
|
|
|
func encodeFaces(e *encoder, frs []faceRun) {
|
|
for _, fr := range frs {
|
|
encodeFaceRun(e, fr)
|
|
}
|
|
}
|
|
|
|
type facesIterator struct {
|
|
faces []faceRun
|
|
// How often have we yet shown the current face?
|
|
numCurrentFaceShown int
|
|
curFace int
|
|
}
|
|
|
|
func (fi *facesIterator) next() (ok bool) {
|
|
if len(fi.faces) == 0 {
|
|
return false
|
|
}
|
|
fi.curFace = fi.faces[0].face
|
|
fi.numCurrentFaceShown++
|
|
|
|
// Advance fs if needed.
|
|
if fi.faces[0].count <= fi.numCurrentFaceShown {
|
|
fi.faces = fi.faces[1:]
|
|
fi.numCurrentFaceShown = 0
|
|
}
|
|
|
|
return true
|
|
}
|
|
|
|
func decodePointsCompressed(d *decoder, level int, target []Point) {
|
|
faces := decodeFaces(len(target), d)
|
|
|
|
piCoder := newNthDerivativeCoder(derivativeEncodingOrder)
|
|
qiCoder := newNthDerivativeCoder(derivativeEncodingOrder)
|
|
|
|
iter := facesIterator{faces: faces}
|
|
for i := range target {
|
|
decodeFn := decodePointCompressed
|
|
if i == 0 {
|
|
decodeFn = decodeFirstPointFixedLength
|
|
}
|
|
pi, qi := decodeFn(d, level, piCoder, qiCoder)
|
|
if ok := iter.next(); !ok && d.err == nil {
|
|
d.err = fmt.Errorf("ran out of faces at target %d", i)
|
|
return
|
|
}
|
|
target[i] = Point{facePiQitoXYZ(iter.curFace, pi, qi, level)}
|
|
}
|
|
|
|
numOffCenter := int(d.readUvarint())
|
|
if d.err != nil {
|
|
return
|
|
}
|
|
if numOffCenter > len(target) {
|
|
d.err = fmt.Errorf("numOffCenter = %d, should be at most len(target) = %d", numOffCenter, len(target))
|
|
return
|
|
}
|
|
for i := 0; i < numOffCenter; i++ {
|
|
idx := int(d.readUvarint())
|
|
if d.err != nil {
|
|
return
|
|
}
|
|
if idx >= len(target) {
|
|
d.err = fmt.Errorf("off center index = %d, should be < len(target) = %d", idx, len(target))
|
|
return
|
|
}
|
|
target[idx].X = d.readFloat64()
|
|
target[idx].Y = d.readFloat64()
|
|
target[idx].Z = d.readFloat64()
|
|
}
|
|
}
|
|
|
|
func decodeFirstPointFixedLength(d *decoder, level int, piCoder, qiCoder *nthDerivativeCoder) (pi, qi uint32) {
|
|
bytesToRead := (level + 7) / 8 * 2
|
|
var interleaved uint64
|
|
for i := 0; i < bytesToRead; i++ {
|
|
rr := d.readUint8()
|
|
interleaved |= (uint64(rr) << uint(i*8))
|
|
}
|
|
|
|
piCoded, qiCoded := deinterleaveUint32(interleaved)
|
|
|
|
return uint32(piCoder.decode(int32(piCoded))), uint32(qiCoder.decode(int32(qiCoded)))
|
|
}
|
|
|
|
func zigzagEncode(x int32) uint32 {
|
|
return (uint32(x) << 1) ^ uint32(x>>31)
|
|
}
|
|
|
|
func zigzagDecode(x uint32) int32 {
|
|
return int32((x >> 1) ^ uint32((int32(x&1)<<31)>>31))
|
|
}
|
|
|
|
func decodePointCompressed(d *decoder, level int, piCoder, qiCoder *nthDerivativeCoder) (pi, qi uint32) {
|
|
interleavedZigZagEncodedDerivPiQi := d.readUvarint()
|
|
piZigzag, qiZigzag := deinterleaveUint32(interleavedZigZagEncodedDerivPiQi)
|
|
return uint32(piCoder.decode(zigzagDecode(piZigzag))), uint32(qiCoder.decode(zigzagDecode(qiZigzag)))
|
|
}
|
|
|
|
// We introduce a new coordinate system (pi, qi), which is (si, ti)
|
|
// with the bits that are constant for cells of that level shifted
|
|
// off to the right.
|
|
// si = round(s * 2^31)
|
|
// pi = si >> (31 - level)
|
|
// = floor(s * 2^level)
|
|
// If the point has been snapped to the level, the bits that are
|
|
// shifted off will be a 1 in the msb, then 0s after that, so the
|
|
// fractional part discarded by the cast is (close to) 0.5.
|
|
|
|
// stToPiQi returns the value transformed to the PiQi coordinate space.
|
|
func stToPiQi(s float64, level uint) uint32 {
|
|
return uint32(s * float64(int(1)<<level))
|
|
}
|
|
|
|
// siTiToPiQi returns the value transformed into the PiQi coordinate spade.
|
|
// encodeFirstPointFixedLength encodes the return value using level bits,
|
|
// so we clamp si to the range [0, 2**level - 1] before trying to encode
|
|
// it. This is okay because if si == maxSiTi, then it is not a cell center
|
|
// anyway and will be encoded separately as an off-center point.
|
|
func siTitoPiQi(siTi uint32, level int) uint32 {
|
|
s := uint(siTi)
|
|
const max = maxSiTi - 1
|
|
if s > max {
|
|
s = max
|
|
}
|
|
|
|
return uint32(s >> (maxLevel + 1 - uint(level)))
|
|
}
|
|
|
|
// piQiToST returns the value transformed to ST space.
|
|
func piQiToST(pi uint32, level int) float64 {
|
|
// We want to recover the position at the center of the cell. If the point
|
|
// was snapped to the center of the cell, then math.Modf(s * 2^level) == 0.5.
|
|
// Inverting STtoPiQi gives:
|
|
// s = (pi + 0.5) / 2^level.
|
|
return (float64(pi) + 0.5) / float64(int(1)<<uint(level))
|
|
}
|
|
|
|
func facePiQitoXYZ(face int, pi, qi uint32, level int) r3.Vector {
|
|
return faceUVToXYZ(face, stToUV(piQiToST(pi, level)), stToUV(piQiToST(qi, level))).Normalize()
|
|
}
|