ref: 53fa826a8a695bcfade5c47f636f719c71e96b98
dir: /sys/src/cmd/jpg/writepng.c/
/* * See PNG 1.2 spec, also RFC 2083. */ #include <u.h> #include <libc.h> #include <draw.h> #include <memdraw.h> #include <ctype.h> #include <bio.h> #include <flate.h> #include "imagefile.h" enum { IDATSIZE = 20000, FilterNone = 0, }; typedef struct ZlibR ZlibR; typedef struct ZlibW ZlibW; struct ZlibR { uchar *data; int width; int dx; int dy; int x; int y; int pixwid; }; struct ZlibW { Biobuf *io; uchar *buf; uchar *b; uchar *e; }; static ulong *crctab; static uchar PNGmagic[] = { 137, 'P', 'N', 'G', '\r', '\n', 26, '\n'}; static void put4(uchar *a, ulong v) { a[0] = v>>24; a[1] = v>>16; a[2] = v>>8; a[3] = v; } static void chunk(Biobuf *bo, char *type, uchar *d, int n) { uchar buf[4]; ulong crc = 0; if(strlen(type) != 4) return; put4(buf, n); Bwrite(bo, buf, 4); Bwrite(bo, type, 4); Bwrite(bo, d, n); crc = blockcrc(crctab, crc, type, 4); crc = blockcrc(crctab, crc, d, n); put4(buf, crc); Bwrite(bo, buf, 4); } static int zread(void *va, void *buf, int n) { int a, i, pixels, pixwid; uchar *b, *e, *img; ZlibR *z; z = va; pixwid = z->pixwid; b = buf; e = b+n; while(b+pixwid < e){ /* one less for filter alg byte */ if(z->y >= z->dy) break; if(z->x == 0) *b++ = FilterNone; pixels = (e-b)/pixwid; if(pixels > z->dx - z->x) pixels = z->dx - z->x; img = z->data + z->width*z->y + pixwid*z->x; memmove(b, img, pixwid*pixels); if(pixwid == 4){ /* * Convert to non-premultiplied alpha. */ for(i=0; i<pixels; i++, b+=4){ a = b[3]; if(a == 0) b[0] = b[1] = b[2] = 0; else if(a != 255){ if(b[0] >= a) b[0] = a; b[0] = (b[0]*255)/a; if(b[1] >= a) b[1] = a; b[1] = (b[1]*255)/a; if(b[2] >= a) b[2] = a; b[2] = (b[2]*255)/a; } } }else b += pixwid*pixels; z->x += pixels; if(z->x >= z->dx){ z->x = 0; z->y++; } } return b - (uchar*)buf; } static void IDAT(ZlibW *z) { chunk(z->io, "IDAT", z->buf, z->b - z->buf); z->b = z->buf; } static int zwrite(void *va, void *buf, int n) { int m; uchar *b, *e; ZlibW *z; z = va; b = buf; e = b+n; while(b < e){ m = z->e - z->b; if(m > e - b) m = e - b; memmove(z->b, b, m); z->b += m; b += m; if(z->b >= z->e) IDAT(z); } return n; } static Memimage* memRGBA(Memimage *i) { Memimage *ni; char buf[32]; ulong dst; /* * [A]BGR because we want R,G,B,[A] in big-endian order. Sigh. */ chantostr(buf, i->chan); if(strchr(buf, 'a')) dst = ABGR32; else dst = BGR24; if(i->chan == dst) return i; ni = allocmemimage(i->r, dst); if(ni == nil) return ni; memimagedraw(ni, ni->r, i, i->r.min, nil, i->r.min, S); return ni; } char* memwritepng(Biobuf *io, Memimage *m, ImageInfo *II) { int err, n; uchar buf[200], *h; ulong vgamma; Tm *tm; Memimage *rgb; ZlibR zr; ZlibW zw; crctab = mkcrctab(0xedb88320); if(crctab == nil) sysfatal("mkcrctab error"); deflateinit(); rgb = memRGBA(m); if(rgb == nil) return "allocmemimage nil"; Bwrite(io, PNGmagic, sizeof PNGmagic); /* IHDR chunk */ h = buf; put4(h, Dx(m->r)); h += 4; put4(h, Dy(m->r)); h += 4; *h++ = 8; /* 8 bits per channel */ if(rgb->chan == BGR24) *h++ = 2; /* RGB */ else *h++ = 6; /* RGBA */ *h++ = 0; /* compression - deflate */ *h++ = 0; /* filter - none */ *h++ = 0; /* interlace - none */ chunk(io, "IHDR", buf, h-buf); /* time - using now is suspect */ tm = gmtime(time(0)); h = buf; *h++ = (tm->year + 1900)>>8; *h++ = (tm->year + 1900)&0xff; *h++ = tm->mon + 1; *h++ = tm->mday; *h++ = tm->hour; *h++ = tm->min; *h++ = tm->sec; chunk(io, "tIME", buf, h-buf); /* gamma */ if(II->fields_set & II_GAMMA){ vgamma = II->gamma*100000; put4(buf, vgamma); chunk(io, "gAMA", buf, 4); } /* comment */ if(II->fields_set & II_COMMENT){ strncpy((char*)buf, "Comment", sizeof buf); n = strlen((char*)buf)+1; // leave null between Comment and text strncpy((char*)(buf+n), II->comment, sizeof buf - n); chunk(io, "tEXt", buf, n+strlen((char*)buf+n)); } /* image data */ zr.dx = Dx(m->r); zr.dy = Dy(m->r); zr.width = rgb->width * sizeof(ulong); zr.data = rgb->data->bdata; zr.x = 0; zr.y = 0; zr.pixwid = chantodepth(rgb->chan)/8; zw.io = io; zw.buf = malloc(IDATSIZE); if(zw.buf == nil) sysfatal("malloc: %r"); zw.b = zw.buf; zw.e = zw.b + IDATSIZE; if((err=deflatezlib(&zw, zwrite, &zr, zread, 6, 0)) < 0) sysfatal("deflatezlib %s", flateerr(err)); if(zw.b > zw.buf) IDAT(&zw); free(zw.buf); chunk(io, "IEND", nil, 0); if(m != rgb) freememimage(rgb); return nil; }