Why not?

src/cmd/jpg/writeppm.c

@@ -0,0 +1,164 @@
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+#include <memdraw.h>
+#include <bio.h>
+#include "imagefile.h"
+
+#define	MAXLINE	70
+
+/*
+ * Write data
+ */
+static
+char*
+writedata(Biobuf *fd, Image *image, Memimage *memimage)
+{
+	char *err;
+	uchar *data;
+	int i, x, y, ndata, depth, col, pix, xmask, pmask;
+	ulong chan;
+	Rectangle r;
+
+	if(memimage != nil){
+		r = memimage->r;
+		depth = memimage->depth;
+		chan = memimage->chan;
+	}else{
+		r = image->r;
+		depth = image->depth;
+		chan = image->chan;
+	}
+
+	/* 
+	 * Read image data into memory
+	 * potentially one extra byte on each end of each scan line
+	 */
+	ndata = Dy(r)*(2+Dx(r)*depth/8);
+	data = malloc(ndata);
+	if(data == nil)
+		return "WritePPM: malloc failed";
+	if(memimage != nil)
+		ndata = unloadmemimage(memimage, r, data, ndata);
+	else
+		ndata = unloadimage(image, r, data, ndata);
+	if(ndata < 0){
+		err = malloc(ERRMAX);
+		if(err == nil)
+			return "WritePPM: malloc failed";
+		snprint(err, ERRMAX, "WriteGIF: %r");
+		free(data);
+		return err;
+	}
+
+	/* Encode and emit the data */
+	col = 0;
+	switch(chan){
+	case GREY1:
+	case GREY2:
+	case GREY4:
+		pmask = (1<<depth)-1;
+		xmask = 7>>drawlog2[depth];
+		for(y=r.min.y; y<r.max.y; y++){
+			i = (y-r.min.y)*bytesperline(r, depth);
+			for(x=r.min.x; x<r.max.x; x++){
+				pix = (data[i]>>depth*((xmask-x)&xmask))&pmask;
+				if(((x+1)&xmask) == 0)
+					i++;
+				col += Bprint(fd, "%d ", pix);
+				if(col >= MAXLINE-(2+1)){
+					Bprint(fd, "\n");
+					col = 0;
+				}else
+					col += Bprint(fd, " ");
+			}
+		}
+		break;
+	case	GREY8:
+		for(i=0; i<ndata; i++){
+			col += Bprint(fd, "%d ", data[i]);
+			if(col >= MAXLINE-(4+1)){
+				Bprint(fd, "\n");
+				col = 0;
+			}else
+				col += Bprint(fd, " ");
+		}
+		break;
+	case RGB24:
+		for(i=0; i<ndata; i+=3){
+			col += Bprint(fd, "%d %d %d", data[i+2], data[i+1], data[i]);
+			if(col >= MAXLINE-(4+4+4+1)){
+				Bprint(fd, "\n");
+				col = 0;
+			}else
+				col += Bprint(fd, " ");
+		}
+		break;
+	default:
+		return "WritePPM: can't handle channel type";
+	}
+
+	return nil;
+}
+
+static
+char*
+writeppm0(Biobuf *fd, Image *image, Memimage *memimage, Rectangle r, int chan, char *comment)
+{
+	char *err;
+
+	switch(chan){
+	case GREY1:
+		Bprint(fd, "P1\n");
+		break;
+	case GREY2:
+	case GREY4:
+	case	GREY8:
+		Bprint(fd, "P2\n");
+		break;
+	case RGB24:
+		Bprint(fd, "P3\n");
+		break;
+	default:
+		return "WritePPM: can't handle channel type";
+	}
+
+	if(comment!=nil && comment[0]!='\0'){
+		Bprint(fd, "# %s", comment);
+		if(comment[strlen(comment)-1] != '\n')
+			Bprint(fd, "\n");
+	}
+	Bprint(fd, "%d %d\n", Dx(r), Dy(r));
+
+	/* maximum pixel value */
+	switch(chan){
+	case GREY2:
+		Bprint(fd, "%d\n", 3);
+		break;
+	case GREY4:
+		Bprint(fd, "%d\n", 15);
+		break;
+	case	GREY8:
+	case RGB24:
+		Bprint(fd, "%d\n", 255);
+		break;
+	}
+
+	err = writedata(fd, image, memimage);
+
+	Bprint(fd, "\n");
+	Bflush(fd);
+	return err;
+}
+
+char*
+writeppm(Biobuf *fd, Image *image, char *comment)
+{
+	return writeppm0(fd, image, nil, image->r, image->chan, comment);
+}
+
+char*
+memwriteppm(Biobuf *fd, Memimage *memimage, char *comment)
+{
+	return writeppm0(fd, nil, memimage, memimage->r, memimage->chan, comment);
+}