libvips/libvips/create/text.c

/* vips_text
 *
 * Written on: 20/5/04
 * 29/7/04
 *	- !HAVE_PANGOFT2 was broken, thanks Kenneth
 * 15/11/04
 *	- gah, still broken, thanks Stefan
 * 5/4/06
 * 	- return an error for im_text( "" ) rather than trying to make an
 * 	  empty image
 * 2/2/10
 * 	- gtkdoc
 * 3/6/13
 * 	- rewrite as a class
 * 20/9/15 leiyangyou 
 * 	- add @spacing 
 * 29/5/17
 * 	- don't set "font" if unset, it breaks caching
 * 16/7/17 gargsms
 * 	- implement auto fitting of text inside bounds
 * 12/3/18
 * 	- better fitting of fonts with overhanging edges, thanks Adrià 
 * 26/4/18 fangqiao 
 * 	- add fontfile option
 * 5/12/18 
 * 	- fitting mode could set wrong dpi
 * 	- fitting mode leaked
 * 16/3/19
 * 	- add `justify`
 * 	- set Xoffset/Yoffset to ink left/top
 * 27/6/19
 * 	- fitting could occasionally terminate early [levmorozov]
 */

/*

    This file is part of VIPS.

    VIPS is free software; you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
    02110-1301  USA

 */

/*

    These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk

 */

/*
 */
#define DEBUG

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /*HAVE_CONFIG_H*/
#include <vips/intl.h>

#include <stdio.h>
#include <string.h>

#include <vips/vips.h>

#ifdef HAVE_PANGOFT2

#include <pango/pango.h>
#include <pango/pangoft2.h>

#include "pcreate.h"

typedef struct _VipsText {
	VipsCreate parent_instance;

	char *text;
	char *font;
	int width;
	int height;
	int spacing;
	VipsAlign align;
	gboolean justify;
	int dpi;
	char *fontfile;

	FT_Bitmap bitmap;
	PangoContext *context;
	PangoLayout *layout;

} VipsText;

typedef VipsCreateClass VipsTextClass;

G_DEFINE_TYPE( VipsText, vips_text, VIPS_TYPE_CREATE );

/* Just have one of these and reuse it.
 *
 * This does not unref cleanly on many platforms, so we will leak horribly
 * unless we reuse it. Sadly this means vips_text() needs to use a lock 
 * internally to single-thread text rendering.
 */
static PangoFontMap *vips_text_fontmap = NULL;

/* ... single-thread the body of vips_text() with this.
 */
static GMutex *vips_text_lock = NULL; 

static void
vips_text_dispose( GObject *gobject )
{
	VipsText *text = (VipsText *) gobject;

	VIPS_UNREF( text->layout ); 
	VIPS_UNREF( text->context ); 
	VIPS_FREE( text->bitmap.buffer ); 

	G_OBJECT_CLASS( vips_text_parent_class )->dispose( gobject );
}

static PangoLayout *
text_layout_new( PangoContext *context, 
	const char *text, const char *font, int width, int spacing,
	VipsAlign align, gboolean justify )
{
	PangoLayout *layout;
	PangoFontDescription *font_description;
	PangoAlignment palign;

	layout = pango_layout_new( context );
	pango_layout_set_markup( layout, text, -1 );

	font_description = pango_font_description_from_string( font );
	pango_layout_set_font_description( layout, font_description );
	pango_font_description_free( font_description );

	if( width > 0 )
		pango_layout_set_width( layout, width * PANGO_SCALE );

	if( spacing > 0 )
		pango_layout_set_spacing( layout, spacing * PANGO_SCALE );

	switch( align ) {
	case VIPS_ALIGN_LOW:
		palign = PANGO_ALIGN_LEFT;
		break;

	case VIPS_ALIGN_CENTRE:
		palign = PANGO_ALIGN_CENTER;
		break;

	case VIPS_ALIGN_HIGH:
		palign = PANGO_ALIGN_RIGHT;
		break;

	default:
		palign = PANGO_ALIGN_LEFT;
		break;
	}
	pango_layout_set_alignment( layout, palign );

	pango_layout_set_justify( layout, justify );

	return( layout );
}

static int
vips_text_get_extents( VipsText *text, VipsRect *extents )
{
	PangoRectangle ink_rect;
	PangoRectangle logical_rect;

	pango_ft2_font_map_set_resolution( 
		PANGO_FT2_FONT_MAP( vips_text_fontmap ), text->dpi, text->dpi );

	if( !(text->layout = text_layout_new( text->context, 
		text->text, text->font, 
		text->width, text->spacing, text->align, text->justify )) ) 
		return( -1 );

	pango_layout_get_pixel_extents( text->layout, 
		&ink_rect, &logical_rect );
	extents->left = ink_rect.x;
	extents->top = ink_rect.y;
	extents->width = ink_rect.width;
	extents->height = ink_rect.height;

#ifdef DEBUG
	printf( "vips_text_get_extents: dpi = %d\n", text->dpi ); 
	printf( "    ink left = %d, top = %d, width = %d, height = %d\n",
		ink_rect.x, ink_rect.y, ink_rect.width, ink_rect.height );
	printf( "    logical left = %d, top = %d, width = %d, height = %d\n",
		logical_rect.x, logical_rect.y, 
		logical_rect.width, logical_rect.height );
#endif /*DEBUG*/

	return( 0 );
}

/* Return -ve for extents too small, +ve for extents too large.
 */
static int
vips_text_rect_difference( VipsRect *target, VipsRect *extents )
{
	if( vips_rect_includesrect( target, extents ) ) 
		return( -1 );
	else
		return( 1 );
}

/* Adjust text->dpi to try to fit to the bounding box.
 */
static int
vips_text_autofit( VipsText *text )
{
	VipsRect target;
	VipsRect extents;
	int difference;
	int previous_difference;
	int previous_dpi;

	int lower_dpi;
	int upper_dpi;

	/* First, repeatedly double or halve dpi until we pass the correct
	 * value. This will give us a lower and upper bound.
	 */
	target.left = 0;
	target.top = 0;
	target.width = text->width;
	target.height = text->height;
	previous_dpi = -1;

#ifdef DEBUG
	printf( "vips_text_autofit: "
		"target left = %d, top = %d, width = %d, height = %d\n",
		target.left, target.top, target.width, target.height );
#endif /*DEBUG*/

	for(;;) { 
		if( vips_text_get_extents( text, &extents ) )
			return( -1 ); 
		target.left = extents.left;
		target.top = extents.top;
		difference = vips_text_rect_difference( &target, &extents );

		if( previous_dpi == -1 ) {
			previous_dpi = text->dpi;
			previous_difference = difference;
		}

		/* Stop if we straddle the target.
		 */
		if( difference != previous_difference ) 
			break;

		previous_difference = difference;
		previous_dpi = text->dpi;

		text->dpi = difference < 0 ? text->dpi * 2 : text->dpi / 2;

		/* This can happen with fixed-size fonts.
		 */
		if( text->dpi < 2 ||
			text->dpi > 10000 )
			break;
	}

	if( difference < 0 ) {
		/* We've been coming down.
		 */
		lower_dpi = text->dpi;
		upper_dpi = previous_dpi;
	}
	else {
		lower_dpi = previous_dpi;
		upper_dpi = text->dpi;
	}

#ifdef DEBUG
	printf( "vips_text_autofit: lower dpi = %d, upper dpi = %d\n",
		lower_dpi, upper_dpi );
#endif /*DEBUG*/

	/* Refine lower and upper until they are almost touching.
	 */
	while( upper_dpi - lower_dpi > 1 &&
		difference != 0 ) { 
		text->dpi = (upper_dpi + lower_dpi) / 2;
		if( vips_text_get_extents( text, &extents ) )
			return( -1 ); 
		target.left = extents.left;
		target.top = extents.top;
		difference = vips_text_rect_difference( &target, &extents );

		if( difference < 0 ) 
			lower_dpi = text->dpi;
		else
			upper_dpi = text->dpi;
	}

	/* If we've hit the target exactly and quit the loop, diff will be 0
	 * and we can use upper. Otherwise we are straddling the target and we
	 * must take lower.
	 */
	if( difference == 0 ) 
		text->dpi = upper_dpi;
	else 
		text->dpi = lower_dpi;
	g_object_set( text, "autofit_dpi", text->dpi, NULL ); 

#ifdef DEBUG
	printf( "vips_text_autofit: final dpi = %d\n", text->dpi );
#endif /*DEBUG*/

	return( 0 ); 
}

static int
vips_text_build( VipsObject *object )
{
	VipsObjectClass *class = VIPS_OBJECT_GET_CLASS( object );
	VipsCreate *create = VIPS_CREATE( object );
	VipsText *text = (VipsText *) object;

	VipsRect extents;
	int y;

	if( VIPS_OBJECT_CLASS( vips_text_parent_class )->build( object ) )
		return( -1 );

	if( !pango_parse_markup( text->text, -1, 0, NULL, NULL, NULL, NULL ) ) {
		vips_error( class->nickname, 
			"%s", _( "invalid markup in text" ) );
		return( -1 );
	}

	g_mutex_lock( vips_text_lock ); 

	if( !vips_text_fontmap )
		vips_text_fontmap = pango_ft2_font_map_new();

	text->context = pango_font_map_create_context( 
		PANGO_FONT_MAP( vips_text_fontmap ) );

	if( text->fontfile &&
		!FcConfigAppFontAddFile( NULL, 
			(const FcChar8 *) text->fontfile ) ) {
		vips_error( class->nickname, 
			_( "unable to load font \"%s\"" ), text->fontfile );
		g_mutex_unlock( vips_text_lock ); 
		return( -1 );
	}

	/* If our caller set height and not dpi, we adjust dpi until 
	 * we get a fit.
	 */
	if( vips_object_argument_isset( object, "height" ) &&
		!vips_object_argument_isset( object, "dpi" ) ) {
		if( vips_text_autofit( text ) )
			return( -1 );
	}

	/* Layout. Can fail for "", for example.
	 */
	if( vips_text_get_extents( text, &extents ) )
		return( -1 );
	if( extents.width == 0 || 
		extents.height == 0 ) {
		vips_error( class->nickname, "%s", _( "no text to render" ) );
		g_mutex_unlock( vips_text_lock ); 
		return( -1 );
	}

	text->bitmap.width = extents.width;
	text->bitmap.pitch = (text->bitmap.width + 3) & ~3;
	text->bitmap.rows = extents.height;
	if( !(text->bitmap.buffer = 
		VIPS_ARRAY( NULL, 
			text->bitmap.pitch * text->bitmap.rows, VipsPel )) ) {
		g_mutex_unlock( vips_text_lock ); 
		return( -1 );
	}
	text->bitmap.num_grays = 256;
	text->bitmap.pixel_mode = ft_pixel_mode_grays;
	memset( text->bitmap.buffer, 0x00, 
		text->bitmap.pitch * text->bitmap.rows );

	pango_ft2_render_layout( &text->bitmap, text->layout, 
		-extents.left, -extents.top );

	g_mutex_unlock( vips_text_lock ); 

	vips_image_init_fields( create->out,
		text->bitmap.width, text->bitmap.rows, 1, 
		VIPS_FORMAT_UCHAR, VIPS_CODING_NONE, 
		VIPS_INTERPRETATION_MULTIBAND,
		1.0, 1.0 ); 
	vips_image_pipelinev( create->out, 
		VIPS_DEMAND_STYLE_ANY, NULL );
	create->out->Xoffset = extents.left;
	create->out->Yoffset = extents.top;

	for( y = 0; y < text->bitmap.rows; y++ ) 
		if( vips_image_write_line( create->out, y, 
			(VipsPel *) text->bitmap.buffer + 
				y * text->bitmap.pitch ) )
			return( -1 );

	return( 0 );
}

static void *
vips_text_make_lock( void *client )
{
	if( !vips_text_lock ) 
		vips_text_lock = vips_g_mutex_new();

	return( NULL );
}

static void
vips_text_class_init( VipsTextClass *class )
{
	GObjectClass *gobject_class = G_OBJECT_CLASS( class );
	VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS( class );

	static GOnce once = G_ONCE_INIT;

	VIPS_ONCE( &once, vips_text_make_lock, NULL );

	gobject_class->dispose = vips_text_dispose;
	gobject_class->set_property = vips_object_set_property;
	gobject_class->get_property = vips_object_get_property;

	vobject_class->nickname = "text";
	vobject_class->description = _( "make a text image" );
	vobject_class->build = vips_text_build;

	VIPS_ARG_STRING( class, "text", 4, 
		_( "Text" ), 
		_( "Text to render" ),
		VIPS_ARGUMENT_REQUIRED_INPUT,
		G_STRUCT_OFFSET( VipsText, text ),
		NULL ); 

	VIPS_ARG_STRING( class, "font", 5, 
		_( "Font" ), 
		_( "Font to render with" ),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET( VipsText, font ),
		NULL ); 

	VIPS_ARG_INT( class, "width", 6, 
		_( "Width" ), 
		_( "Maximum image width in pixels" ),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET( VipsText, width ),
		0, VIPS_MAX_COORD, 0 );

	VIPS_ARG_INT( class, "height", 7, 
		_( "Height" ), 
		_( "Maximum image height in pixels" ),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET( VipsText, height ),
		0, VIPS_MAX_COORD, 0 );

	VIPS_ARG_ENUM( class, "align", 8, 
		_( "Align" ), 
		_( "Align on the low, centre or high edge" ),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET( VipsText, align ),
		VIPS_TYPE_ALIGN, VIPS_ALIGN_LOW );

	VIPS_ARG_BOOL( class, "justify", 9, 
		_( "Justify" ), 
		_( "Justify lines" ),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET( VipsText, justify ),
		FALSE );

	VIPS_ARG_INT( class, "dpi", 9, 
		_( "DPI" ), 
		_( "DPI to render at" ),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET( VipsText, dpi ),
		1, 1000000, 72 );

	VIPS_ARG_INT( class, "autofit_dpi", 10, 
		_( "Autofit DPI" ), 
		_( "DPI selected by autofit" ),
		VIPS_ARGUMENT_OPTIONAL_OUTPUT,
		G_STRUCT_OFFSET( VipsText, dpi ),
		1, 1000000, 72 );

	VIPS_ARG_INT( class, "spacing", 11, 
		_( "Spacing" ), 
		_( "Line spacing" ),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET( VipsText, spacing ),
		0, 1000000, 0 );

	VIPS_ARG_STRING( class, "fontfile", 12, 
		_( "Font file" ), 
		_( "Load this font file" ),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET( VipsText, fontfile ),
		NULL ); 

}

static void
vips_text_init( VipsText *text )
{
	text->align = VIPS_ALIGN_LOW;
	text->dpi = 72;
	text->bitmap.buffer = NULL;
	VIPS_SETSTR( text->font, "sans 12" ); 
}

#endif /*HAVE_PANGOFT2*/

/**
 * vips_text:
 * @out: (out): output image
 * @text: utf-8 text string to render
 * @...: %NULL-terminated list of optional named arguments
 *
 * Optional arguments:
 *
 * * @font: %gchararray, font to render with
 * * @fontfile: %gchararray, load this font file
 * * @width: %gint, image should be no wider than this many pixels
 * * @height: %gint, image should be no higher than this many pixels
 * * @align: #VipsAlign, left/centre/right alignment
 * * @justify: %gboolean, justify lines
 * * @dpi: %gint, render at this resolution
 * * @autofit_dpi: %gint, read out auto-fitted DPI 
 * * @spacing: %gint, space lines by this in points
 *
 * Draw the string @text to an image. @out is a one-band 8-bit
 * unsigned char image, with 0 for no text and 255 for text. Values between
 * are used for anti-aliasing.
 *
 * @text is the text to render as a UTF-8 string. It can contain Pango markup,
 * for example "&lt;i&gt;The&lt;/i&gt;Guardian".
 *
 * @font is the font to render with, as a fontconfig name. Examples might be
 * "sans 12" or perhaps "bitstream charter bold 10".
 *
 * You can specify a font to load with @fontfile. You'll need to also set the
 * name of the font with @font.
 *
 * @width is the number of pixels to word-wrap at. Lines of text wider than
 * this will be broken at word boundaries. 
 * @align can be used to set the alignment style for multi-line
 * text. Note that the output image can be wider than @width if there are no
 * word breaks, or narrower if the lines don't break exactly at @width. 
 *
 * Set @justify to turn on line justification.
 *
 * @height is the maximum number of pixels high the generated text can be. This
 * only takes effect when @dpi is not set, and @width is set, making a box. 
 * In this case, vips_text() will search for a @dpi and set of line breaks 
 * which will just fit the text into @width and @height.
 *
 * You can use @autofit_dpi to read out the DPI selected by auto fit. 
 *
 * @dpi sets the resolution to render at. "sans 12" at 72 dpi draws characters
 * approximately 12 pixels high. 
 *
 * @spacing sets the line spacing, in points. It would typically be something
 * like font size times 1.2.
 *
 * You can read the coordinate of the top edge of the character from `Xoffset`
 * / `Yoffset`. This can be helpful if you need to line up the output of
 * several vips_text().
 *
 * See also: vips_bandjoin(), vips_composite().
 *
 * Returns: 0 on success, -1 on error
 */
int
vips_text( VipsImage **out, const char *text, ... )
{
	va_list ap;
	int result;

	va_start( ap, text );
	result = vips_call_split( "text", ap, out, text );
	va_end( ap );

	return( result );
}