mirror of
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SPDX is an ISO standard for describing licenses in a computer readable format, which is useful when applying license compliance tools and the like to source code. In addition to ensuring that the Wuffs C distribution is properly annotated to the benefit of projects using Wuffs and SPDX-supporting tools, add it everywhere else where there's a license in this repo for consistency, too.
124 lines
2.6 KiB
Go
124 lines
2.6 KiB
Go
// Copyright 2020 The Wuffs Authors.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//
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// SPDX-License-Identifier: Apache-2.0 OR MIT
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//go:build ignore
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// +build ignore
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package main
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// convert-png-to-wbmp.go decodes PNG from stdin and encodes WBMP Type 0 to
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// stdout.
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//
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// WBMP (Wireless Bitmap) is described in Section 6 and Appendix A of
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// http://www.wapforum.org/what/technical/SPEC-WAESpec-19990524.pdf
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//
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// Usage: go run convert-png-to-wbmp.go < foo.png > foo.wbmp
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import (
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"bufio"
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"errors"
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"image"
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"image/draw"
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"image/png"
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"os"
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)
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func main() {
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if err := main1(); err != nil {
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os.Stderr.WriteString(err.Error() + "\n")
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os.Exit(1)
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}
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}
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func main1() error {
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src, err := png.Decode(os.Stdin)
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if err != nil {
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return err
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}
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b := src.Bounds()
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dst := image.NewGray(b)
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draw.Draw(dst, b, src, b.Min, draw.Src)
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w := bufio.NewWriter(os.Stdout)
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defer w.Flush()
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// TypeField, FixHeaderField.
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w.WriteString("\x00\x00")
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// Width, height.
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if err := writeMultiByteInteger(w, b.Dx()); err != nil {
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return err
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}
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if err := writeMultiByteInteger(w, b.Dy()); err != nil {
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return err
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}
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// Rows.
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for y := b.Min.Y; y < b.Max.Y; y++ {
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i := dst.PixOffset(b.Min.X, y)
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j := dst.PixOffset(b.Max.X, y)
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if err := writeRow(w, dst.Pix[i:j]); err != nil {
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return err
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}
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}
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return nil
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}
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func writeMultiByteInteger(w *bufio.Writer, x int) error {
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if x < 0 {
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return errors.New("cannot encode negative integer")
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}
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n := 1
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for z := x; z > 0x7F; n, z = n+1, z>>7 {
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}
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for i := n - 1; i >= 0; i-- {
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c := (x >> uint(7*i)) & 0x7F
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if i > 0 {
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c |= 0x80
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}
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if err := w.WriteByte(byte(c)); err != nil {
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return err
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}
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}
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return nil
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}
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func writeRow(w *bufio.Writer, row []byte) error {
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// Pack as many complete groups of 8 pixels as we can.
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n := len(row) / 8
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for i := 0; i < n; i++ {
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row8 := row[i*8 : i*8+8]
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c := ((row8[0] & 0x80) >> 0) |
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((row8[1] & 0x80) >> 1) |
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((row8[2] & 0x80) >> 2) |
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((row8[3] & 0x80) >> 3) |
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((row8[4] & 0x80) >> 4) |
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((row8[5] & 0x80) >> 5) |
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((row8[6] & 0x80) >> 6) |
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((row8[7] & 0x80) >> 7)
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if err := w.WriteByte(c); err != nil {
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return err
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}
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}
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row = row[8*n:]
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// Pack up to 7 remaining pixels.
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if len(row) > 0 {
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c := byte(0)
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for i, x := range row {
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c |= (x & 0x80) >> uint(i)
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}
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if err := w.WriteByte(c); err != nil {
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return err
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}
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}
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return nil
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}
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