ref: 57741d473f9d5165d142b165bd837984f6428c66
dir: /sys/src/cmd/venti/srv/png.c/
#include "stdinc.h" #include "dat.h" #include "fns.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 { Hio *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(Hio *io, char *type, uchar *d, int n) { uchar buf[4]; ulong crc = 0; if(strlen(type) != 4) return; put4(buf, n); hwrite(io, buf, 4); hwrite(io, type, 4); hwrite(io, d, n); crc = blockcrc(crctab, crc, type, 4); crc = blockcrc(crctab, crc, d, n); put4(buf, crc); hwrite(io, 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){ 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 && 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; qlock(&memdrawlock); ni = allocmemimage(i->r, dst); if(ni) memimagedraw(ni, ni->r, i, i->r.min, nil, i->r.min, S); qunlock(&memdrawlock); return ni; } int writepng(Hio *io, Memimage *m) { static int first = 1; static QLock lk; uchar buf[200], *h; Memimage *rgb; ZlibR zr; ZlibW zw; if(first){ qlock(&lk); if(first){ deflateinit(); crctab = mkcrctab(0xedb88320); first = 0; } qunlock(&lk); } rgb = memRGBA(m); if(rgb == nil) return -1; hwrite(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); /* 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 = vtmalloc(IDATSIZE); zw.b = zw.buf; zw.e = zw.b + IDATSIZE; if(deflatezlib(&zw, zwrite, &zr, zread, 6, 0) < 0){ free(zw.buf); return -1; } if(zw.b > zw.buf) IDAT(&zw); free(zw.buf); chunk(io, "IEND", nil, 0); if(m != rgb){ qlock(&memdrawlock); freememimage(rgb); qunlock(&memdrawlock); } return 0; }