render dithered text with libvips

watermark_fax2.c

/* watermark a fax image with vips8 C
 *
 * compile with

 	gcc -g -Wall watermark_fax.c `pkg-config vips --cflags --libs`

 */

#include <vips/vips.h>

int
main( int argc, char **argv )
{
	VipsImage *base;
	VipsImage **t;
	VipsImage *in;
	VipsImage *dither;
	VipsImage *text;
	VipsImage *overlay;

	if( VIPS_INIT( argv[0] ) )
		vips_error_exit( NULL );

	if( argc != 4 ) 
		vips_error_exit( "usage: %s in-file out-file \"message\"", 
			argv[0] ); 

	base = vips_image_new();
	t = (VipsImage **) vips_object_local_array( VIPS_OBJECT( base ), 12 );

	if( !(t[0] = vips_image_new_from_file( argv[1], 
		"access", VIPS_ACCESS_SEQUENTIAL,
		NULL )) ) {
		g_object_unref( base );
		vips_error_exit( NULL );
	}
	in = t[0];

	if( !(t[1] = vips_image_new_matrixv( 6, 6,
		255.0,   0.0,   0.0,   0.0, 255.0,   0.0,
		  0.0, 255.0,   0.0, 255.0,   0.0,   0.0,
		  0.0,   0.0, 255.0,   0.0,   0.0,   0.0,
		  0.0, 255.0,   0.0, 255.0,   0.0,   0.0,
		255.0,   0.0,   0.0,   0.0, 255.0,   0.0,
		  0.0,   0.0,   0.0,   0.0,   0.0, 255.0 )) ||
		vips_cast( t[1], &t[2], VIPS_FORMAT_UCHAR, NULL ) ) { 
		g_object_unref( base );
		vips_error_exit( NULL );
	}
	dither = t[2];

	if( vips_text( &t[3], argv[3],
			"width", 500,
			"dpi", 300,
			NULL ) ||
		vips_replicate( dither, &t[4], 
			1 + t[3]->Xsize / dither->Xsize, 
			1 + t[3]->Ysize / dither->Ysize, NULL ) ||
		vips_crop( t[4], &t[5], 0, 0, 
			t[3]->Xsize, t[3]->Ysize, NULL ) ||
		vips_andimage( t[5], t[3], &t[6], NULL ) ) {
		g_object_unref( base );
		vips_error_exit( NULL );
	}
	text = t[6];

	if( vips_embed( text, &t[7], 100, 100, 
			text->Xsize + 200, text->Ysize + 200, NULL ) ||
		vips_replicate( t[7], &t[8], 
			1 + in->Xsize / t[7]->Xsize, 
			1 + in->Ysize / t[7]->Ysize, NULL ) ||
		vips_crop( t[8], &t[9], 0, 0, 
			in->Xsize, in->Ysize, NULL ) ) {
		g_object_unref( base );
		vips_error_exit( NULL );
	}
	overlay = t[9];

	/* EOR the image and overlay and write to output.
	 */
	if( vips_eorimage( in, overlay, &t[10], NULL ) ||
		vips_image_write_to_file( t[10], argv[2], NULL ) ) { 
		g_object_unref( base );
		vips_error_exit( NULL );
	}

	g_object_unref( base );

	return( 0 );
}