write frames to png files and some clean up

2026-10-24 10:12:36 +00:00 · 2021-05-28 23:34:08 +03:00
parent 1aa42cde33
commit 249ac3dea7
3 changed files with 243 additions and 39 deletions
@@ -0,0 +1,194 @@
+package main
+
+import (
+	"bytes"
+	"compress/zlib"
+	"encoding/binary"
+	"hash/crc32"
+	"io/fs"
+	"os"
+)
+
+func writeHeader(pngFile *os.File) {
+	header := []byte{0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a}
+	_, err := pngFile.Write(header)
+	if err != nil {
+		panic(err)
+	}
+}
+
+func writeIHDR(pngFile *os.File, width uint16, height uint16) {
+	chunkLength := []byte{0x00, 0x00, 0x00, 0x0D} // always 13
+	IHDR := []byte{0x49, 0x48, 0x44, 0x52}        // IHDR string
+	bitDepth := byte(0x8)                         // number of bits per sample or per palette index (always 8 for indexed-color)
+	colorType := byte(0x3)                        // 3 is Indexed-color which is what's used for GIFs. this also means a PLTE chunk needs to exist
+	compressionMethod := byte(0x0)                // always 0
+	filterMethod := byte(0x0)                     // always 0
+	interlaceMethod := byte(0x0)                  // 0 or 1
+	hash := make([]byte, 4)                       // crc-32 hash of the previous 13 bytes
+
+	chunkData := make([]byte, 13)
+
+	binary.BigEndian.PutUint32(chunkData[0:4], uint32(width))
+	binary.BigEndian.PutUint32(chunkData[4:8], uint32(height))
+	chunkData[8] = bitDepth
+	chunkData[9] = colorType
+	chunkData[10] = compressionMethod
+	chunkData[11] = filterMethod
+	chunkData[12] = interlaceMethod
+
+	binary.BigEndian.PutUint32(hash, crc32.Update(crc32.ChecksumIEEE(IHDR), crc32.IEEETable, chunkData))
+
+	_, err := pngFile.Write(chunkLength)
+	if err != nil {
+		panic(err)
+	}
+	_, err = pngFile.Write(IHDR)
+	if err != nil {
+		panic(err)
+	}
+	_, err = pngFile.Write(chunkData)
+	if err != nil {
+		panic(err)
+	}
+	_, err = pngFile.Write(hash)
+	if err != nil {
+		panic(err)
+	}
+}
+
+func writePLTE(pngFile *os.File, palette Palette) {
+	chunkLength := make([]byte, 4)
+	PLTE := []byte{0x50, 0x4C, 0x54, 0x45}
+	hash := make([]byte, 4)
+
+	binary.BigEndian.PutUint32(chunkLength, uint32(len(palette)*3))
+	binary.BigEndian.PutUint32(hash, crc32.Update(crc32.ChecksumIEEE(PLTE), crc32.IEEETable, palette.MarshalBinary()))
+
+	_, err := pngFile.Write(chunkLength)
+	if err != nil {
+		panic(err)
+	}
+	_, err = pngFile.Write(PLTE)
+	if err != nil {
+		panic(err)
+	}
+	_, err = pngFile.Write(palette.MarshalBinary())
+	if err != nil {
+		panic(err)
+	}
+	_, err = pngFile.Write(hash)
+	if err != nil {
+		panic(err)
+	}
+}
+
+func writetRNS(pngFile *os.File, transparencyIndex int) {
+	chunkLength := make([]byte, 4)
+	tRNS := []byte{0x74, 0x52, 0x4E, 0x53}
+	hash := make([]byte, 4)
+
+	binary.BigEndian.PutUint32(chunkLength, uint32(transparencyIndex)+1)
+
+	data := make([]byte, transparencyIndex+1)
+	for i := 0; i < transparencyIndex; i++ {
+		data[i] = 0xFF
+	}
+
+	data[transparencyIndex] = 0
+
+	binary.BigEndian.PutUint32(hash, crc32.Update(crc32.ChecksumIEEE(tRNS), crc32.IEEETable, data))
+
+	_, err := pngFile.Write(chunkLength)
+	if err != nil {
+		panic(err)
+	}
+	_, err = pngFile.Write(tRNS)
+	if err != nil {
+		panic(err)
+	}
+	_, err = pngFile.Write(data)
+	if err != nil {
+		panic(err)
+	}
+	_, err = pngFile.Write(hash)
+	if err != nil {
+		panic(err)
+	}
+}
+
+func serialize(data []byte, width int, height int) []byte {
+	b := make([]byte, 0, (width+1)*height)
+	for i := 0; i < height; i++ {
+		b = append(b, 0)
+		b = append(b, data[width*i:width*(i+1)]...)
+	}
+	return b
+}
+
+func writeIDAT(pngFile *os.File, data []byte, width uint16, height uint16) {
+	chunkLength := make([]byte, 4)
+	IDAT := []byte{0x49, 0x44, 0x41, 0x54}
+	hash := make([]byte, 4)
+
+	binary.BigEndian.PutUint32(chunkLength, uint32(len(data)))
+	binary.BigEndian.PutUint32(hash, crc32.Update(crc32.ChecksumIEEE(IDAT), crc32.IEEETable, data))
+
+	_, err := pngFile.Write(chunkLength)
+	if err != nil {
+		panic(err)
+	}
+	_, err = pngFile.Write(IDAT)
+	if err != nil {
+		panic(err)
+	}
+	var buf bytes.Buffer
+	writer, err := zlib.NewWriterLevel(&buf, zlib.BestCompression)
+	if err != nil {
+		panic(err)
+	}
+	defer writer.Close()
+	_, err = writer.Write(serialize(data, int(width), int(height)))
+	if err != nil {
+		panic(err)
+	}
+	writer.Flush()
+	_, err = pngFile.Write(buf.Bytes())
+	if err != nil {
+		panic(err)
+	}
+	_, err = pngFile.Write(hash)
+	if err != nil {
+		panic(err)
+	}
+}
+
+func writeIEND(pngFile *os.File) {
+	chunkLength := []byte{0x00, 0x00, 0x00, 0x00}
+	IEND := []byte{0x49, 0x45, 0x4E, 0x44}
+	hash := make([]byte, 4)
+	binary.BigEndian.PutUint32(hash, crc32.Update(crc32.ChecksumIEEE(IEND), crc32.IEEETable, nil))
+
+	IENDChunk := append(chunkLength, append(IEND, hash...)...)
+	_, err := pngFile.Write(IENDChunk)
+	if err != nil {
+		panic(err)
+	}
+}
+
+func WriteToPNG(data []byte, palette Palette, fileName string, width uint16, height uint16, transparenyIndex int) {
+	pngFile, err := os.OpenFile(fileName, os.O_CREATE|os.O_WRONLY, fs.FileMode(0755))
+	if err != nil {
+		panic(err)
+	}
+
+	writeHeader(pngFile)
+	writeIHDR(pngFile, width, height)
+	writePLTE(pngFile, palette)
+	if transparenyIndex != -1 {
+		writetRNS(pngFile, transparenyIndex)
+	}
+	writeIDAT(pngFile, data, width, height)
+	writeIEND(pngFile)
+	pngFile.Close()
+}