go/src/image/png/writer.go

type Encoder …

type EncoderBufferPool …

type EncoderBuffer …

type encoder …

type CompressionLevel …

const DefaultCompression …

const NoCompression …

const BestSpeed …

const BestCompression …

type opaquer …

// Returns whether or not the image is fully opaque.
func opaque(m image.Image) bool { … }

// The absolute value of a byte interpreted as a signed int8.
func abs8(d uint8) int { … }

func (e *encoder) writeChunk(b []byte, name string) { … }

func (e *encoder) writeIHDR() { … }

func (e *encoder) writePLTEAndTRNS(p color.Palette) { … }

// An encoder is an io.Writer that satisfies writes by writing PNG IDAT chunks,
// including an 8-byte header and 4-byte CRC checksum per Write call. Such calls
// should be relatively infrequent, since writeIDATs uses a [bufio.Writer].
//
// This method should only be called from writeIDATs (via writeImage).
// No other code should treat an encoder as an io.Writer.
func (e *encoder) Write(b []byte) (int, error) { … }

// Chooses the filter to use for encoding the current row, and applies it.
// The return value is the index of the filter and also of the row in cr that has had it applied.
func filter(cr *[nFilter][]byte, pr []byte, bpp int) int { … }

func (e *encoder) writeImage(w io.Writer, m image.Image, cb int, level int) error { … }

// Write the actual image data to one or more IDAT chunks.
func (e *encoder) writeIDATs() { … }

// This function is required because we want the zero value of
// Encoder.CompressionLevel to map to zlib.DefaultCompression.
func levelToZlib(l CompressionLevel) int { … }

func (e *encoder) writeIEND() { … }

// Encode writes the Image m to w in PNG format. Any Image may be
// encoded, but images that are not [image.NRGBA] might be encoded lossily.
func Encode(w io.Writer, m image.Image) error { … }

// Encode writes the Image m to w in PNG format.
func (enc *Encoder) Encode(w io.Writer, m image.Image) error { … }