FLTK 1.4.0: Fl_Image Class Reference

Base class for image caching, scaling and drawing. More...

#include <Fl_Image.H>

Inheritance diagram for Fl_Image:

Public Member Functions
virtual class Fl_Shared_Image *	as_shared_image ()
	Returns whether an image is an Fl_Shared_Image or not. More...

virtual void	color_average (Fl_Color c, float i)
	The color_average() method averages the colors in the image with the provided FLTK color value. More...

Fl_Image *	copy () const
	Creates a copy of the image in the same size. More...

virtual Fl_Image *	copy (int W, int H) const
	Creates a resized copy of the image. More...

int	count () const
	Returns the number of data values associated with the image. More...

int	d () const
	Returns the image depth. More...

const char const	data () const
	Returns a pointer to the current image data array. More...

int	data_h () const
	Returns the height of the image data.

int	data_w () const
	Returns the width of the image data.

virtual void	desaturate ()
	The desaturate() method converts an image to grayscale. More...

void	draw (int X, int Y)
	Draws the image to the current drawing surface. More...

virtual void	draw (int X, int Y, int W, int H, int cx=0, int cy=0)
	Draws the image to the current drawing surface with a bounding box. More...

int	fail () const
	Returns a value that is not 0 if there is currently no image available. More...

	Fl_Image (int W, int H, int D)
	The constructor creates an empty image with the specified width, height, and depth. More...

int	h () const
	Returns the current image drawing height in FLTK units. More...

void	inactive ()
	The inactive() method calls color_average(FL_BACKGROUND_COLOR, 0.33f) to produce an image that appears grayed out. More...

virtual void	label (Fl_Menu_Item *m)
	This method is an obsolete way to set the image attribute of a menu item. More...

virtual void	label (Fl_Widget *w)
	This method is an obsolete way to set the image attribute of a widget or menu item. More...

int	ld () const
	Returns the current line data size in bytes. More...

virtual void	release ()
	Releases an Fl_Image - the same as '`delete` `this'`. More...

virtual void	scale (int width, int height, int proportional=1, int can_expand=0)
	Sets the drawing size of the image. More...

virtual void	uncache ()
	If the image has been cached for display, delete the cache data. More...

int	w () const
	Returns the current image drawing width in FLTK units. More...

virtual	~Fl_Image ()
	The destructor is a virtual method that frees all memory used by the image.

Static Public Member Functions
static Fl_Labeltype	define_FL_IMAGE_LABEL ()

static Fl_RGB_Scaling	RGB_scaling ()
	Returns the currently used RGB image scaling method.

static void	RGB_scaling (Fl_RGB_Scaling)
	Sets the RGB image scaling method used for copy(int, int). More...

static Fl_RGB_Scaling	scaling_algorithm ()
	Gets what algorithm is used when resizing a source image to draw it.

static void	scaling_algorithm (Fl_RGB_Scaling algorithm)
	Sets what algorithm is used when resizing a source image to draw it. More...

Static Public Attributes
static const int	ERR_FILE_ACCESS = -2

static const int	ERR_FORMAT = -3

static const int	ERR_MEMORY_ACCESS = -4

static const int	ERR_NO_IMAGE = -1

static bool	register_images_done = false
	True after fl_register_images() was called, false before.

Protected Member Functions
void	d (int D)
	Sets the current image depth.

void	data (const char const p, int c)
	Sets the current data pointer and count of pointers in the array. More...

void	draw_empty (int X, int Y)
	The protected method draw_empty() draws a box with an X in it. More...

int	draw_scaled (int X, int Y, int W, int H)
	Draw the image to the current drawing surface rescaled to a given width and height. More...

void	h (int H)
	Sets the height of the image data. More...

void	ld (int LD)
	Sets the current line data size in bytes. More...

void	w (int W)
	Sets the width of the image data. More...

Static Protected Member Functions
static void	labeltype (const Fl_Label *lo, int lx, int ly, int lw, int lh, Fl_Align la)

static void	measure (const Fl_Label *lo, int &lw, int &lh)

Friends
class	Fl_Graphics_Driver

Detailed Description

Base class for image caching, scaling and drawing.

Fl_Image is the base class used for caching, scaling and drawing all kinds of images in FLTK. This class keeps track of common image data such as the pixels, colormap, width, height, and depth. Virtual methods are used to provide type-specific image handling.

Each image possesses two (width, height) pairs:

The width and height of the raw image data are returned by data_w() and data_h(). These values are set when the image is created and remain unchanged.
The width and height of the area filled by the image when it gets drawn are returned by w() and h(). These values are equal to data_w() and data_h() when the image is created and can be changed by the scale() member function.

Since the Fl_Image class does not support image drawing by itself, calling the Fl_Image::draw() method results in a box with an X in it being drawn instead.

Constructor & Destructor Documentation

◆ Fl_Image()

Fl_Image::Fl_Image	(	int	W,
		int	H,
		int	D
	)

The constructor creates an empty image with the specified width, height, and depth.

The width and height are in pixels. The depth is 0 for bitmaps, 1 for pixmap (colormap) images, and 1 to 4 for color images.

Member Function Documentation

◆ as_shared_image()

virtual class Fl_Shared_Image * Fl_Image::as_shared_image ( )

inlinevirtual

Returns whether an image is an Fl_Shared_Image or not.

This virtual method returns a pointer to an Fl_Shared_Image if this object is an instance of Fl_Shared_Image or NULL if not. This can be used to detect if a given Fl_Image object is a shared image, i.e. derived from Fl_Shared_Image.

Since: 1.4.0

Reimplemented in Fl_Shared_Image.

◆ color_average()

void Fl_Image::color_average	(	Fl_Color	c,
		float	i
	)

virtual

The color_average() method averages the colors in the image with the provided FLTK color value.

The first argument specifies the FLTK color to be used.

The second argument specifies the amount of the original image to combine with the color, so a value of 1.0 results in no color blend, and a value of 0.0 results in a constant image of the specified color.

An internal copy is made of the original image data before changes are applied, to avoid modifying the original image data in memory.

Reimplemented in Fl_Anim_GIF_Image, Fl_RGB_Image, Fl_Pixmap, Fl_Shared_Image, Fl_SVG_Image, and Fl_Tiled_Image.

◆ copy() [1/2]

Fl_Image * Fl_Image::copy ( ) const

inline

Creates a copy of the image in the same size.

The new image should be released when you are done with it.

This does exactly the same as 'Fl_Image::copy(int W, int H) const' where W and H are the width and height of the source image, respectively. This applies also to all subclasses of Fl_Image in the FLTK library.

The following two copy() calls are equivalent:

Fl_Image *img1 = new Fl_Image(...);
// ...
Fl_Image *img2 = img1->copy();
Fl_Image *img3 = img1->copy(img1->w(), img1->h())

For details see 'Fl_Image::copy(int w, int h) const'.

See also: Fl_Image::release()

Note: Since FLTK 1.4.0 this method is 'const'. If you derive your own class from Fl_Image or any subclass your overridden methods of 'Fl_Image::copy() const' and 'Fl_Image::copy(int, int) const' must also be 'const' for inheritance to work properly. This is different than in FLTK 1.3.x and earlier where these methods have not been 'const'.

◆ copy() [2/2]

Fl_Image * Fl_Image::copy	(	int	W,
		int	H
	)		const

virtual

Creates a resized copy of the image.

It is recommended not to call this member function to reduce the size of an image to the size of the area where this image will be drawn, and to use Fl_Image::scale() instead.

The new image should be released when you are done with it.

Note: since FLTK 1.4.0 you can use Fl_Image::release() for all types of images (i.e. all subclasses of Fl_Image) instead of operator delete for Fl_Image's and Fl_Image::release() for Fl_Shared_Image's.

The new image data will be converted to the requested size. RGB images are resized using the algorithm set by Fl_Image::RGB_scaling().

For the new image the following equations are true:

w() == data_w() == W
h() == data_h() == H

Parameters

[in] W,H Requested width and height of the new image

Note: The returned image can be safely cast to the same image type as that of the source image provided this type is one of Fl_RGB_Image, Fl_SVG_Image, Fl_Pixmap, Fl_Bitmap, Fl_Tiled_Image, Fl_Anim_GIF_Image and Fl_Shared_Image. Returned objects copied from images of other, derived, image classes belong to the parent class appearing in this list. For example, the copy of an Fl_GIF_Image is an object of class Fl_Pixmap.; Since FLTK 1.4.0 this method is 'const'. If you derive your own class from Fl_Image or any subclass your overridden methods of 'Fl_Image::copy() const' and 'Fl_Image::copy(int, int) const' must also be 'const' for inheritance to work properly. This is different than in FLTK 1.3.x and earlier where these methods have not been 'const'.

Reimplemented in Fl_Anim_GIF_Image, Fl_Bitmap, Fl_RGB_Image, Fl_Pixmap, Fl_Shared_Image, Fl_SVG_Image, and Fl_Tiled_Image.

◆ count()

int Fl_Image::count ( ) const

inline

Returns the number of data values associated with the image.

The value will be 0 for images with no associated data, 1 for bitmap and color images, and greater than 2 for pixmap images.

See also: data()

◆ d()

int Fl_Image::d ( ) const

inline

Returns the image depth.

The return value will be 0 for bitmaps, 1 for pixmaps, and 1 to 4 for color images.

◆ data() [1/2]

const char *const * Fl_Image::data ( ) const

inline

Returns a pointer to the current image data array.

There can be 0, 1, or more pointers to actual image data in an image.

Use the count() method to find the size of the data array. You must not dereference the data() pointer if count() equals zero.

Note: data() may return NULL.

Example:

Fl_RGB_Image has exactly one pointer which points at the R, G, B [, A] data array of the image. The total size of this array depends on several attributes like data_w(), data_h(), d() and ld() and is basically data_w() * data_h() * d() but there are exceptions if ld() is non-zero: see description of ld(). Since FLTK 1.4.0 w() and h() are no longer significant for the image data size if scale() has been called on the image to set a different display size.

Other image types have different numbers and types of data pointers which are implementation details and not documented here.

See also: count(), w(), h(), data_w(), data_h(), d(), ld()

◆ data() [2/2]

void Fl_Image::data	(	const char const	p,
		int	c
	)

inlineprotected

Sets the current data pointer and count of pointers in the array.

There can be 0, 1, or more pointers to actual image data in an image.

See also: const char* const* data(), count(), w(), h(), data_w(), data_h(), d(), ld()

◆ desaturate()

void Fl_Image::desaturate ( )

virtual

The desaturate() method converts an image to grayscale.

If the image contains an alpha channel (depth = 4), the alpha channel is preserved.

An internal copy is made of the original image data before changes are applied, to avoid modifying the original image data in memory.

Reimplemented in Fl_Anim_GIF_Image, Fl_RGB_Image, Fl_Pixmap, Fl_Shared_Image, Fl_SVG_Image, and Fl_Tiled_Image.

◆ draw() [1/2]

void Fl_Image::draw	(	int	X,
		int	Y
	)

inline

Draws the image to the current drawing surface.

Parameters

X,Y	specify the upper-lefthand corner of the image.

◆ draw() [2/2]

void Fl_Image::draw	(	int	X,
		int	Y,
		int	W,
		int	H,
		int	cx = `0`,
		int	cy = `0`
	)

virtual

Draws the image to the current drawing surface with a bounding box.

Arguments X,Y,W,H specify a bounding box for the image, with the origin (upper-left corner) of the image offset by the cx and cy arguments.

In other words: fl_push_clip(X,Y,W,H) is applied, the image is drawn with its upper-left corner at X-cx,Y-cy and its own width and height, fl_pop_clip() is applied.

Reimplemented in Fl_Anim_GIF_Image, Fl_Bitmap, Fl_RGB_Image, Fl_Pixmap, Fl_Shared_Image, Fl_SVG_Image, and Fl_Tiled_Image.

◆ draw_empty()

void Fl_Image::draw_empty	(	int	X,
		int	Y
	)

protected

The protected method draw_empty() draws a box with an X in it.

It can be used to draw any image that lacks image data.

◆ draw_scaled()

int Fl_Image::draw_scaled	(	int	X,
		int	Y,
		int	W,
		int	H
	)

protected

Draw the image to the current drawing surface rescaled to a given width and height.

Intended for internal use by the FLTK library.

Parameters

X,Y	position of the image's top-left
W,H	width and height for the drawn image

Returns: 1

Deprecated:: Only for API compatibility with FLTK 1.3.4.

◆ fail()

int Fl_Image::fail ( ) const

Returns a value that is not 0 if there is currently no image available.

Example use:

// [..]
  Fl_Box box(X, Y, W, H);
  Fl_JPEG_Image jpg("/tmp/foo.jpg");
  switch (jpg.fail()) {
    case Fl_Image::ERR_NO_IMAGE:
    case Fl_Image::ERR_FILE_ACCESS:
      fl_alert("/tmp/foo.jpg: %s", strerror(errno));    // shows actual os error to user
      exit(1);
    case Fl_Image::ERR_FORMAT:
      fl_alert("/tmp/foo.jpg: couldn't decode image");
      exit(1);
  }
  box.image(jpg);

Returns: Image load failure if non-zero

Return values

0	the image was loaded successfully
ERR_NO_IMAGE	no image was found
ERR_FILE_ACCESS	there was a file access related error (errno should be set)
ERR_FORMAT	image decoding failed
ERR_MEMORY_ACCESS	image decoder tried to access memory outside of given memory block

◆ h() [1/2]

int Fl_Image::h ( ) const

inline

Returns the current image drawing height in FLTK units.

The values of h() and data_h() are identical unless scale() has been called after which they may differ.

◆ h() [2/2]

void Fl_Image::h ( int H )

inlineprotected

Sets the height of the image data.

This protected function sets both image heights: the height of the image data returned by data_h() and the image drawing height in FLTK units returned by h().

◆ inactive()

void Fl_Image::inactive ( )

inline

The inactive() method calls color_average(FL_BACKGROUND_COLOR, 0.33f) to produce an image that appears grayed out.

An internal copy is made of the original image before changes are applied, to avoid modifying the original image.

Note: The RGB color of FL_BACKGROUND_COLOR may change when the connection to the display is made. See fl_open_display().

◆ label() [1/2]

void Fl_Image::label ( Fl_Menu_Item * m )

virtual

This method is an obsolete way to set the image attribute of a menu item.

Deprecated:: Please use Fl_Menu_Item::image() instead.

Reimplemented in Fl_Bitmap, Fl_RGB_Image, and Fl_Pixmap.

◆ label() [2/2]

void Fl_Image::label ( Fl_Widget * widget )

virtual

This method is an obsolete way to set the image attribute of a widget or menu item.

Deprecated:: Please use Fl_Widget::image() or Fl_Widget::deimage() instead.

Reimplemented in Fl_Bitmap, Fl_RGB_Image, and Fl_Pixmap.

◆ ld() [1/2]

int Fl_Image::ld ( ) const

inline

Returns the current line data size in bytes.

See also: ld(int)

◆ ld() [2/2]

void Fl_Image::ld ( int LD )

inlineprotected

Sets the current line data size in bytes.

Color images may contain extra data (padding) that is included after every line of color image data and is normally not present.

If LD is zero, then line data size is assumed to be data_w() * d() bytes.

If LD is non-zero, then it must be positive and larger than data_w() * d() to account for the extra data per line.

◆ release()

virtual void Fl_Image::release ( )

inlinevirtual

Releases an Fl_Image - the same as 'delete this'.

This virtual method is for almost all image classes the same as calling

delete image;

where image is an Fl_Image * pointer.

However, for subclass Fl_Shared_Image and its subclasses this virtual method is reimplemented and maintains shared images.

This virtual method makes it possible to destroy all image types in the same way by calling

image->release();

Reasoning: If you have an 'Fl_Image *' base class pointer and don't know if the object is one of the class Fl_Shared_Image or any other subclass of Fl_Image (for instance Fl_RGB_Image) then you can't just use operator delete since this is not appropriate for Fl_Shared_Image objects.

The virtual method release() handles this properly.

Since: 1.4.0 in the base class Fl_Image and virtual in Fl_Shared_Image

Reimplemented in Fl_Shared_Image.

◆ RGB_scaling()

void Fl_Image::RGB_scaling ( Fl_RGB_Scaling method )

static

Sets the RGB image scaling method used for copy(int, int).

Applies to all RGB images, defaults to FL_RGB_SCALING_NEAREST.

◆ scale()

void Fl_Image::scale	(	int	width,
		int	height,
		int	proportional = `1`,
		int	can_expand = `0`
	)

virtual

Sets the drawing size of the image.

This function controls the values returned by member functions w() and h() which in turn control how the image is drawn: the full image data (whose size is given by data_w() and data_h()) are drawn scaled to an area of the drawing surface sized at w() x h() FLTK units. This can make a difference if the drawing surface has more than 1 pixel per FLTK unit because the image can be drawn at the full resolution of the drawing surface. Examples of such drawing surfaces: HiDPI displays, laser printers, PostScript files, PDF printers.

Parameters

width,height	maximum values, in FLTK units, that w() and h() should return
proportional	if not null, keep the values returned by w() and h() proportional to data_w() and data_h()
can_expand	if null, the values returned by w() and h() will not be larger than data_w() and data_h(), respectively

Note: This function generally changes the values returned by the w() and h() member functions. In contrast, the values returned by data_w() and data_h() remain unchanged.

Version: 1.4 (1.3.4 and FL_ABI_VERSION for Fl_Shared_Image only)

Example code: scale an image to fit in a box

Fl_Box *b = ...  // a box
Fl_Image *img = new Fl_PNG_Image("/path/to/picture.png"); // read a picture file
// set the drawing size of the image to the size of the box keeping its aspect ratio
img->scale(b->w(), b->h());
b->image(img); // use the image as the box image

◆ scaling_algorithm()

static void Fl_Image::scaling_algorithm ( Fl_RGB_Scaling algorithm )

inlinestatic

Sets what algorithm is used when resizing a source image to draw it.

The default algorithm is FL_RGB_SCALING_BILINEAR. Drawing an Fl_Image is sometimes performed by first resizing the source image and then drawing the resized copy. This occurs, e.g., when drawing to screen under X11 without Xrender support after having called scale(). This function controls what method is used when the image to be resized is an Fl_RGB_Image.

Version: 1.4

◆ uncache()

void Fl_Image::uncache ( )

virtual

If the image has been cached for display, delete the cache data.

This allows you to change the data used for the image and then redraw it without recreating an image object.

Reimplemented in Fl_Anim_GIF_Image, Fl_Bitmap, Fl_RGB_Image, Fl_Pixmap, and Fl_Shared_Image.

◆ w() [1/2]

int Fl_Image::w ( ) const

inline

Returns the current image drawing width in FLTK units.

The values of w() and data_w() are identical unless scale() has been called after which they may differ.

◆ w() [2/2]

void Fl_Image::w ( int W )

inlineprotected

Sets the width of the image data.

This protected function sets both image widths: the width of the image data returned by data_w() and the image drawing width in FLTK units returned by w().

The documentation for this class was generated from the following files:

Fl_Image.H
Fl_Image.cxx

Public Member Functions

Static Public Member Functions

Static Public Attributes

Protected Member Functions

Static Protected Member Functions

Friends

Detailed Description

Constructor & Destructor Documentation

◆ Fl_Image()

Member Function Documentation

◆ as_shared_image()

◆ color_average()

◆ copy() [1/2]

◆ copy() [2/2]

◆ count()

◆ d()

◆ data() [1/2]

◆ data() [2/2]

◆ desaturate()

◆ draw() [1/2]

◆ draw() [2/2]

◆ draw_empty()

◆ draw_scaled()

◆ fail()

◆ h() [1/2]

◆ h() [2/2]

◆ inactive()

◆ label() [1/2]

◆ label() [2/2]

◆ ld() [1/2]

◆ ld() [2/2]

◆ release()

◆ RGB_scaling()

◆ scale()

◆ scaling_algorithm()

◆ uncache()

◆ w() [1/2]

◆ w() [2/2]