diff options
Diffstat (limited to 'png.go')
| -rw-r--r-- | png.go | 212 |
1 files changed, 212 insertions, 0 deletions
@@ -0,0 +1,212 @@ +/* + * Copyright (c) 2013-2016 Kurt Jung (Gmail: kurt.w.jung) + * + * Permission to use, copy, modify, and distribute this software for any + * purpose with or without fee is hereby granted, provided that the above + * copyright notice and this permission notice appear in all copies. + * + * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES + * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF + * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR + * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES + * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN + * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF + * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. + */ + +package gofpdf + +import ( + "bytes" + "fmt" + "strings" +) + +func (f *Fpdf) pngColorSpace(ct byte) (colspace string, colorVal int) { + colorVal = 1 + switch ct { + case 0, 4: + colspace = "DeviceGray" + case 2, 6: + colspace = "DeviceRGB" + colorVal = 3 + case 3: + colspace = "Indexed" + default: + f.err = fmt.Errorf("unknown color type in PNG buffer: %d", ct) + } + return +} + +func (f *Fpdf) parsepngstream(buf *bytes.Buffer, readdpi bool) (info *ImageInfoType) { + info = f.newImageInfo() + // Check signature + if string(buf.Next(8)) != "\x89PNG\x0d\x0a\x1a\x0a" { + f.err = fmt.Errorf("not a PNG buffer") + return + } + // Read header chunk + _ = buf.Next(4) + if string(buf.Next(4)) != "IHDR" { + f.err = fmt.Errorf("incorrect PNG buffer") + return + } + w := f.readBeInt32(buf) + h := f.readBeInt32(buf) + bpc := f.readByte(buf) + if bpc > 8 { + f.err = fmt.Errorf("16-bit depth not supported in PNG file") + } + ct := f.readByte(buf) + var colspace string + var colorVal int + colspace, colorVal = f.pngColorSpace(ct) + if f.err != nil { + return + } + if f.readByte(buf) != 0 { + f.err = fmt.Errorf("'unknown compression method in PNG buffer") + return + } + if f.readByte(buf) != 0 { + f.err = fmt.Errorf("'unknown filter method in PNG buffer") + return + } + if f.readByte(buf) != 0 { + f.err = fmt.Errorf("interlacing not supported in PNG buffer") + return + } + _ = buf.Next(4) + dp := sprintf("/Predictor 15 /Colors %d /BitsPerComponent %d /Columns %d", colorVal, bpc, w) + // Scan chunks looking for palette, transparency and image data + pal := make([]byte, 0, 32) + var trns []int + data := make([]byte, 0, 32) + loop := true + for loop { + n := int(f.readBeInt32(buf)) + // dbg("Loop [%d]", n) + switch string(buf.Next(4)) { + case "PLTE": + // dbg("PLTE") + // Read palette + pal = buf.Next(n) + _ = buf.Next(4) + case "tRNS": + // dbg("tRNS") + // Read transparency info + t := buf.Next(n) + if ct == 0 { + trns = []int{int(t[1])} // ord(substr($t,1,1))); + } else if ct == 2 { + trns = []int{int(t[1]), int(t[3]), int(t[5])} // array(ord(substr($t,1,1)), ord(substr($t,3,1)), ord(substr($t,5,1))); + } else { + pos := strings.Index(string(t), "\x00") + if pos >= 0 { + trns = []int{pos} // array($pos); + } + } + _ = buf.Next(4) + case "IDAT": + // dbg("IDAT") + // Read image data block + data = append(data, buf.Next(n)...) + _ = buf.Next(4) + case "IEND": + // dbg("IEND") + loop = false + case "pHYs": + // dbg("pHYs") + // png files theoretically support different x/y dpi + // but we ignore files like this + // but if they're the same then we can stamp our info + // object with it + x := int(f.readBeInt32(buf)) + y := int(f.readBeInt32(buf)) + units := buf.Next(1)[0] + // fmt.Printf("got a pHYs block, x=%d, y=%d, u=%d, readdpi=%t\n", + // x, y, int(units), readdpi) + // only modify the info block if the user wants us to + if x == y && readdpi { + switch units { + // if units is 1 then measurement is px/meter + case 1: + info.dpi = float64(x) / 39.3701 // inches per meter + default: + info.dpi = float64(x) + } + } + _ = buf.Next(4) + default: + // dbg("default") + _ = buf.Next(n + 4) + } + if loop { + loop = n > 0 + } + } + if colspace == "Indexed" && len(pal) == 0 { + f.err = fmt.Errorf("missing palette in PNG buffer") + } + info.w = float64(w) + info.h = float64(h) + info.cs = colspace + info.bpc = int(bpc) + info.f = "FlateDecode" + info.dp = dp + info.pal = pal + info.trns = trns + // dbg("ct [%d]", ct) + if ct >= 4 { + // Separate alpha and color channels + var err error + data, err = sliceUncompress(data) + if err != nil { + f.err = err + return + } + var color, alpha bytes.Buffer + if ct == 4 { + // Gray image + width := int(w) + height := int(h) + length := 2 * width + var pos, elPos int + for i := 0; i < height; i++ { + pos = (1 + length) * i + color.WriteByte(data[pos]) + alpha.WriteByte(data[pos]) + elPos = pos + 1 + for k := 0; k < width; k++ { + color.WriteByte(data[elPos]) + alpha.WriteByte(data[elPos+1]) + elPos += 2 + } + } + } else { + // RGB image + width := int(w) + height := int(h) + length := 4 * width + var pos, elPos int + for i := 0; i < height; i++ { + pos = (1 + length) * i + color.WriteByte(data[pos]) + alpha.WriteByte(data[pos]) + elPos = pos + 1 + for k := 0; k < width; k++ { + color.Write(data[elPos : elPos+3]) + alpha.WriteByte(data[elPos+3]) + elPos += 4 + } + } + } + data = sliceCompress(color.Bytes()) + info.smask = sliceCompress(alpha.Bytes()) + if f.pdfVersion < "1.4" { + f.pdfVersion = "1.4" + } + } + info.data = data + return +} |