FLTK 1.3.4: Fl_Image Class Reference

FLTK 1.3.4

Public Member Functions | Static Public Member Functions | Static Public Attributes | Protected Member Functions | Static Protected Member Functions | List of all members
Fl_Image Class Reference

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

`#include <Fl_Image.H>`

Inheritance diagram for Fl_Image:

## Public Member Functions
virtual void | color_average (Fl_Color c, float i)
| The color_average() method averages the colors in the image with the FLTK color value c. More...
virtual Fl_Image * | copy (int W, int H)
| The copy() method creates a copy of the specified image. More...
Fl_Image * | copy ()
| The copy() method creates a copy of the specified image. More...
int | count () const
| The count() method returns the number of data values associated with the image. More...
int | d () const
| Returns the current image depth. More...
const char *const * | data () const
| Returns a pointer to the current image data array. More...
virtual void | desaturate ()
| The desaturate() method converts an image to grayscale. More...
virtual void | draw (int X, int Y, int W, int H, int cx=0, int cy=0)
| Draws the image with a bounding box. More...
void | draw (int X, int Y)
| Draws the image. More...
int | fail ()
| 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 height in pixels.
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_Widget *w)
| The label() methods are an obsolete way to set the image attribute of a widget or menu item. More...
virtual void | label (Fl_Menu_Item *m)
| The label() methods are 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 | uncache ()
| If the image has been cached for display, delete the cache data. More...
int | w () const
| Returns the current image width in pixels.
virtual | ~Fl_Image ()
| The destructor is a virtual method that frees all memory used by the image.

## Static Public Member Functions
static void | RGB_scaling (Fl_RGB_Scaling)
| Sets the RGB image scaling method used for copy(int, int). More...
static Fl_RGB_Scaling | RGB_scaling ()
| Returns the currently used RGB image scaling method. More...

## Static Public Attributes
static const int | ERR_FILE_ACCESS = -2
static const int | ERR_FORMAT = -3
static const int | ERR_NO_IMAGE = -1

## Protected Member Functions
void | d (int D)
| Sets the current image depth.
void | data (const char *const *p, int c)
| Sets the current array pointer and count of pointers in the array.
void | draw_empty (int X, int Y)
| The protected method draw_empty() draws a box with an X in it. More...
void | h (int H)
| Sets the current image height in pixels.
void | ld (int LD)
| Sets the current line data size in bytes. More...
void | w (int W)
| Sets the current image width in pixels.

## 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)

## Detailed Description

Base class for image caching and drawing.

Fl_Image is the base class used for caching 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.

Since the Fl_Image class does not support image drawing by itself, calling the 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

## § 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 FLTK color value c.

The i 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 before changes are applied, to avoid modifying the original image.

Reimplemented in Fl_RGB_Image, Fl_Shared_Image, Fl_Pixmap, and Fl_Tiled_Image.

## § copy() [1/2]

Fl_Image * Fl_Image::copy | ( | int | W,
|  | int | H
| ) |  |
| virtual

The copy() method creates a copy of the specified image.

If the width and height are provided, the image is resized to the specified size. The image should be deleted (or in the case of Fl_Shared_Image, released) when you are done with it.

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

## § copy() [2/2]

Fl_Image* Fl_Image::copy | ( |  | ) |
| inline

The copy() method creates a copy of the specified image.

If the width and height are provided, the image is resized to the specified size. The image should be deleted (or in the case of Fl_Shared_Image, released) when you are done with it.

## § count()

int Fl_Image::count | ( |  | ) | const
| inline

The count() method 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.

## § d()

int Fl_Image::d | ( |  | ) | const
| inline

Returns the current image depth.

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

## § data()

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

Returns a pointer to the current image data array.

Use the count() method to find the size of the data array.

## § 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 before changes are applied, to avoid modifying the original image.

Reimplemented in Fl_RGB_Image, Fl_Shared_Image, Fl_Pixmap, and Fl_Tiled_Image.

## § draw() [1/2]

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

Draws the image 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_RGB_Image, Fl_Shared_Image, Fl_Pixmap, Fl_Bitmap, and Fl_Tiled_Image.

## § draw() [2/2]

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

Draws the image.

This form specifies the upper-lefthand corner of the 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.

## § fail()

int Fl_Image::fail | ( |  | ) |

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
  ERR_NO_IMAGE if no image was found
  ERR_FILE_ACCESS if there was a file access related error (errno should be set)
  ERR_FORMAT if image decoding failed.

## § 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.

## § label() [1/2]

void Fl_Image::label | ( | Fl_Widget * | widget | ) |
| virtual

The label() methods are an obsolete way to set the image attribute of a widget or menu item.

Use the image() or deimage() methods of the Fl_Widget and Fl_Menu_Item classes instead.

Reimplemented in Fl_RGB_Image, Fl_Pixmap, and Fl_Bitmap.

## § label() [2/2]

void Fl_Image::label | ( | Fl_Menu_Item * | m | ) |
| virtual

The label() methods are an obsolete way to set the image attribute of a widget or menu item.

Use the image() or deimage() methods of the Fl_Widget and Fl_Menu_Item classes instead.

Reimplemented in Fl_RGB_Image, Fl_Pixmap, and Fl_Bitmap.

## § ld() [1/2]

void Fl_Image::ld | ( | int | LD | ) |
| inlineprotected

Sets the current line data size in bytes.

Color images may contain extra data 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 w() * d() bytes.

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

## § ld() [2/2]

int Fl_Image::ld | ( |  | ) | const
| inline

Returns the current line data size in bytes.

See also
  ld(int)

## § RGB_scaling() [1/2]

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.

## § RGB_scaling() [2/2]

Fl_RGB_Scaling Fl_Image::RGB_scaling | ( |  | ) |
| static

Returns the currently used RGB image scaling method.

## § 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_RGB_Image, Fl_Shared_Image, Fl_Pixmap, and Fl_Bitmap.

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

- Fl_Image.H
- Fl_Image.cxx

- © 1998-2016 by Bill Spitzak and others.