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add support for alpha

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This commit is contained in:
rsc 2005-02-15 05:04:18 +00:00
parent 429f8aa4c1
commit 0cbccd3a0e
1 changed files with 46 additions and 13 deletions
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59
src/cmd/jpg/writepng.c
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@ -21,6 +21,7 @@ typedef struct ZlibR{
int width;
int nrow, ncol;
int row, col; // next pixel to send
int pixwid;
} ZlibR;
typedef struct ZlibW{
@ -68,19 +69,42 @@ zread(void *va, void *buf, int n)
int ncol = z->ncol;
uchar *b = buf, *e = b+n, *img;
int pixels; // number of pixels in row that can be sent now
while(b+3 <= e){ // loop over image rows
int i, a, pixwid;
pixwid = z->pixwid;
while(b+pixwid <= e){ // loop over image rows
if(z->row >= nrow)
break;
if(z->col==0)
*b++ = FilterNone;
pixels = (e-b)/3;
pixels = (e-b)/pixwid;
if(pixels > ncol - z->col)
pixels = ncol - z->col;
img = z->data + z->width * z->row + 3 * z->col;
img = z->data + z->width * z->row + pixwid * z->col;
memmove(b, img, 3*pixels);
b += 3*pixels;
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 == 255 || a == 0)
;
else{
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->col += pixels;
if(z->col >= ncol){
@ -119,17 +143,25 @@ zwrite(void *va, void *buf, int n)
}
static Memimage*
memRGB(Memimage *i)
memRGBA(Memimage *i)
{
Memimage *ni;
char buf[32];
ulong dst;
/*
* BGR24 because we want R,G,B in big-endian order. Sigh.
* [A]BGR because we want R,G,B,[A] in big-endian order. Sigh.
*/
if(i->chan == BGR24)
chantostr(buf, i->chan);
if(strchr(buf, 'a'))
dst = ABGR32;
else
dst = BGR24;
if(i->chan == dst)
return i;
ni = allocmemimage(i->r, BGR24);
ni = allocmemimage(i->r, dst);
if(ni == nil)
return ni;
memimagedraw(ni, ni->r, i, i->r.min, nil, i->r.min, S);
@ -149,7 +181,7 @@ memwritepng(Biobuf *bo, Memimage *r, ImageInfo *II)
Tm *tm;
Memimage *rgb;
rgb = memRGB(r);
rgb = memRGBA(r);
if(rgb == nil)
return "allocmemimage nil";
crctab = mkcrctab(0xedb88320);
@ -163,7 +195,7 @@ memwritepng(Biobuf *bo, Memimage *r, ImageInfo *II)
put4(h, ncol); h += 4;
put4(h, nrow); h += 4;
*h++ = 8; // bit depth = 24 bit per pixel
*h++ = 2; // color type = rgb
*h++ = rgb->chan==BGR24 ? 2 : 6; // color type = rgb
*h++ = 0; // compression method = deflate
*h++ = 0; // filter method
*h++ = 0; // interlace method = no interlace
@ -199,6 +231,7 @@ memwritepng(Biobuf *bo, Memimage *r, ImageInfo *II)
zr.width = rgb->width * sizeof(ulong);
zr.data = rgb->data->bdata;
zr.row = zr.col = 0;
zr.pixwid = chantodepth(rgb->chan)/8;
zw.bo = bo;
zw.buf = malloc(IDATSIZE);
zw.b = zw.buf;