shithub: imgtools

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resample: preserve original format if possible, fix alpha channel

--- a/resample.c

+++ b/resample.c

@@ -26,7 +26,7 @@

 static void

 usage(void)

 {

-	fprint(2, "usage: %s [-x size] [-y size] [-f filter] [-c colorspace]\n", argv0);

+	fprint(2, "usage: %s [-P] [-x size] [-y size] [-f filter] [-c colorspace]\n", argv0);

 	exits("usage");

 }

@@ -36,12 +36,15 @@

 	Memimage *a, *b;

 	u8int *in, *out;

 	char *flts, *s, *csps;

-	int n, w, h, bp;

-	int ow, oh, obp;

+	int alphai, flags;

+	int w, h, ow, oh;

 	int wp, hp, f, c;

+	int n, bp, to;

 	ow = oh = 0;

 	wp = hp = 0;

+	alphai = STBIR_ALPHA_CHANNEL_NONE;

+	flags = STBIR_FLAG_ALPHA_PREMULTIPLIED;

 	flts = filters[STBIR_FILTER_MITCHELL];

 	csps = cspaces[STBIR_COLORSPACE_LINEAR];

 	ARGBEGIN{

@@ -59,6 +62,9 @@

 	case 'c':

 		csps = EARGF(usage());

 		break;

+	case 'P':

+		flags &= ~STBIR_FLAG_ALPHA_PREMULTIPLIED;

+		break;

 	default:

 		usage();

 	}ARGEND

@@ -87,13 +93,55 @@

 	memimageinit();

 	if((a = readmemimage(0)) == nil)

 		sysfatal("memory");

-	if(a->chan != RGB24){

-		if((b = allocmemimage(a->r, RGB24)) == nil)

+

+	bp = 0;

+again:

+	switch(a->chan){

+	case GREY8:

+		bp = 1;

+		break;

+	case RGB24:

+		bp = 3;

+		break;

+	case RGBA32:

+		bp = 4;

+		alphai = 3;

+		break;

+	case ARGB32:

+	case XRGB32:

+		bp = 4;

+		alphai = 0;

+		break;

+

+	case GREY1:

+	case GREY2:

+	case GREY4:

+		to = GREY8;

+		goto convert;

+	case CMAP8:

+	case RGB15:

+	case RGB16:

+		to = RGB24;

+		goto convert;

+	case BGR24:

+		to = RGB24;

+		goto convert;

+	case ABGR32:

+		to = ARGB32;

+		goto convert;

+	case XBGR32:

+		to = XRGB32;

+convert:

+		if((b = allocmemimage(a->r, to)) == nil)

 			sysfatal("memory");

 		memimagedraw(b, a->r, a, ZP, nil, ZP, S);

 		freememimage(a);

 		a = b;

+		goto again;

+	default:

+		sysfatal("invalid chan %#lux", a->chan);

 	}

+

 	w = Dx(a->r);

 	h = Dy(a->r);

 	if(wp)

@@ -106,24 +154,23 @@

 		ow = oh*w/h;

 	if(ow < 1 || oh < 1)

 		sysfatal("invalid size: %dx%d", ow, oh);

-	bp = 3;

 	n = w*h*bp;

 	if((in = malloc(w*h*bp)) == nil)

 		sysfatal("%r");

 	if(unloadmemimage(a, a->r, in, n) < 0)

 		sysfatal("%r");

-	obp = 3;

-	if((out = malloc(ow*oh*obp)) == nil)

+	if((out = malloc(ow*oh*bp)) == nil)

 		sysfatal("memory");

 	stbir_resize_uint8_generic(

 		in, w, h, w*bp,

-		out, ow, oh, ow*obp,

-		3, -1, 0,

+		out, ow, oh, ow*bp,

+		bp, alphai, flags,

 		STBIR_EDGE_CLAMP, f, c,

 		NULL);

-	if((b = allocmemimage(Rect(0,0,ow,oh), RGB24)) == nil)

+	free(in);

+	if((b = allocmemimage(Rect(0,0,ow,oh), a->chan)) == nil)

 		sysfatal("%r");

-	loadmemimage(b, b->r, out, ow*oh*obp);

+	loadmemimage(b, b->r, out, ow*oh*bp);

 	writememimage(1, b);

 	exits(nil);