Typedefs | Enumerations | Functions
Image Object Functions

Here are grouped together functions used to create and manipulate image objects. More...

Typedefs

typedef void(* Evas_Object_Image_Pixels_Get_Cb) (void *data, Evas_Object *o)
 Function signature for the evas object pixels get callback function. More...
 
typedef enum _Evas_Colorspace Evas_Colorspace
 Colorspaces for pixel data supported by Evas. More...
 

Enumerations

enum  _Evas_Colorspace {
  EVAS_COLORSPACE_ARGB8888,
  EVAS_COLORSPACE_YCBCR422P601_PL,
  EVAS_COLORSPACE_YCBCR422P709_PL,
  EVAS_COLORSPACE_RGB565_A5P,
  EVAS_COLORSPACE_GRY8,
  EVAS_COLORSPACE_YCBCR422601_PL,
  EVAS_COLORSPACE_YCBCR420NV12601_PL,
  EVAS_COLORSPACE_YCBCR420TM12601_PL,
  EVAS_COLORSPACE_AGRY88,
  EVAS_COLORSPACE_ETC1,
  EVAS_COLORSPACE_RGB8_ETC2,
  EVAS_COLORSPACE_RGBA8_ETC2_EAC,
  EVAS_COLORSPACE_ETC1_ALPHA,
  EVAS_COLORSPACE_RGB_S3TC_DXT1,
  EVAS_COLORSPACE_RGBA_S3TC_DXT1,
  EVAS_COLORSPACE_RGBA_S3TC_DXT2,
  EVAS_COLORSPACE_RGBA_S3TC_DXT3,
  EVAS_COLORSPACE_RGBA_S3TC_DXT4,
  EVAS_COLORSPACE_RGBA_S3TC_DXT5
}
 Colorspaces for pixel data supported by Evas. More...
 

Functions

Eina_Bool evas_object_image_extension_can_load_get (const char *file)
 Check if a file extension may be supported by Image Object Functions. More...
 
Eina_Bool evas_object_image_extension_can_load_fast_get (const char *file)
 Check if a file extension may be supported by Image Object Functions. More...
 
Evas_Objectevas_object_image_add (Evas *e)
 Creates a new image object on the given Evas e canvas. More...
 
Evas_Objectevas_object_image_filled_add (Evas *e)
 Creates a new image object that automatically scales its bound image to the object's area, on both axis. More...
 
void evas_object_image_memfile_set (Evas_Object *obj, void *data, int size, char *format, char *key)
 Sets the data for an image from memory to be loaded. More...
 
void evas_object_image_native_surface_set (Evas_Object *obj, Evas_Native_Surface *surf)
 Set the native surface of a given image of the canvas. More...
 
void evas_object_image_preload (Evas_Object *obj, Eina_Bool cancel)
 Preload an image object's image data in the background. More...
 
Eina_Bool evas_object_image_source_unset (Evas_Object *obj)
 Clear the source object on a proxy image object. More...
 
void evas_object_image_alpha_mask_set (Evas_Object *obj, Eina_Bool ismask)
 Enable an image to be used as an alpha mask. More...
 
void evas_object_image_file_set (Eo *obj, const char *file, const char *key)
 Set the source file from where an image object must fetch the real image data (it may be an Eet file, besides pure image ones). More...
 
void evas_object_image_file_get (const Eo *obj, const char **file, const char **key)
 Retrieve the source file from where an image object is to fetch the real image data (it may be an Eet file, besides pure image ones). More...
 
Eina_Bool evas_object_image_save (const Eo *obj, const char *file, const char *key, const char *flags)
 Save the given image object's contents to an (image) file. More...
 
Eina_Bool evas_object_image_animated_get (const Eo *obj)
 Check if an image object can be animated (have multiple frames) More...
 
void evas_object_image_load_size_set (Eo *obj, int w, int h)
 Set the load size of a given image object's source image. More...
 
void evas_object_image_load_size_get (const Eo *obj, int *w, int *h)
 Get the load size of a given image object's source image. More...
 
void evas_object_image_smooth_scale_set (Eo *obj, Eina_Bool smooth_scale)
 Sets whether to use high-quality image scaling algorithm on the given image object. More...
 
Eina_Bool evas_object_image_smooth_scale_get (const Eo *obj)
 Retrieves whether the given image object is using high-quality image scaling algorithm. More...
 

Detailed Description

Here are grouped together functions used to create and manipulate image objects.

They are available to whichever occasion one needs complex imagery on a GUI that could not be achieved by the other Evas' primitive object types, or to make image manipulations.

Evas will support whichever image file types it was compiled with support to (its image loaders) – check your software packager for that information and see evas_object_image_extension_can_load_get().

Image object basics

The most common use of image objects – to display an image on the canvas – is achieved by a common function triplet:

img = evas_object_image_add(canvas);
evas_object_image_file_set(img, "path/to/img", NULL);
evas_object_image_fill_set(img, 0, 0, w, h);

The first function, naturally, is creating the image object. Then, one must set an source file on it, so that it knows where to fetch image data from. Next, one must set how to fill the image object's area with that given pixel data. One could use just a sub-region of the original image or even have it tiled repeatedly on the image object. For the common case of having the whole source image to be displayed on the image object, stretched to the destination's size, there's also a function helper, to be used instead of evas_object_image_fill_set():

evas_object_image_filled_set(img, EINA_TRUE);

See those functions' documentation for more details.

Scale and resizing

Resizing of image objects will scale their respective source images to their areas, if they are set to "fill" the object's area (evas_object_image_filled_set()). If the user wants any control on the aspect ratio of an image for different sizes, he/she has to take care of that themselves. There are functions to make images to get loaded scaled (up or down) in memory, already, if the user is going to use them at pre-determined sizes and wants to save computations.

Evas has even a scale cache, which will take care of caching scaled versions of images with more often usage/hits. Finally, one can have images being rescaled smoothly by Evas (more computationally expensive) or not.

Performance hints

When dealing with image objects, there are some tricks to boost the performance of your application, if it does intense image loading and/or manipulations, as in animations on a UI.

Load hints

In image viewer applications, for example, the user will be looking at a given image, at full size, and will desire that the navigation to the adjacent images on his/her album be fluid and fast. Thus, while displaying a given image, the program can be on the background loading the next and previous images already, so that displaying them on the sequence is just a matter of repainting the screen (and not decoding image data).

Evas addresses this issue with image pre-loading. The code for the situation above would be something like the following:

evas_object_image_file_set(prev, "/path/to/prev", NULL);
evas_object_image_file_set(next, "/path/to/next", NULL);

If you're loading images which are too big, consider setting previously it's loading size to something smaller, in case you won't expose them in real size. It may speed up the loading considerably:

//to load a scaled down version of the image in memory, if that's
//the size you'll be displaying it anyway
evas_object_image_load_scale_down_set(img, zoom);
//optional: if you know you'll be showing a sub-set of the image's
//pixels, you can avoid loading the complementary data
evas_object_image_load_region_set(img, x, y, w, h);

Refer to Elementary's Photocam widget for a high level (smart) object which does lots of loading speed-ups for you.

Animation hints

If you want to animate image objects on a UI (what you'd get by concomitant usage of other libraries, like Ecore and Edje), there are also some tips on how to boost the performance of your application. If the animation involves resizing of an image (thus, re-scaling), you'd better turn off smooth scaling on it during the animation, turning it back on afterwards, for less computations. Also, in this case you'd better flag the image object in question not to cache scaled versions of it:

evas_object_image_scale_hint_set(wd->img, EVAS_IMAGE_SCALE_HINT_DYNAMIC);
// resizing takes place in between
evas_object_image_scale_hint_set(wd->img, EVAS_IMAGE_SCALE_HINT_STATIC);

Finally, movement of opaque images through the canvas is less expensive than of translucid ones, because of blending computations.

Borders

Evas provides facilities for one to specify an image's region to be treated specially – as "borders". This will make those regions be treated specially on resizing scales, by keeping their aspect. This makes setting frames around other objects on UIs easy. See the following figures for a visual explanation:
Full-size Full-size

Manipulating pixels

Evas image objects can be used to manipulate raw pixels in many ways. The meaning of the data in the pixel arrays will depend on the image's color space, be warned (see next section). You can set your own data as an image's pixel data, fetch an image's pixel data for saving/altering, convert images between different color spaces and even advanced operations like setting a native surface as image objects' data.

Color spaces

Image objects may return or accept "image data" in multiple formats. This is based on the color space of an object. Here is a rundown on formats:

Warning
We don't guarantee any proper results if you create a Image object without setting the evas engine.

Some examples on this group of functions can be found here.

Typedef Documentation

typedef void(* Evas_Object_Image_Pixels_Get_Cb) (void *data, Evas_Object *o)

Function signature for the evas object pixels get callback function.

See also
evas_object_image_pixels_get()

By data it will be passed the private data. By o it will be passed the Evas_Object image on which the pixels are requested.

Colorspaces for pixel data supported by Evas.

Colorspaces for pixel data supported by Evas

Enumeration Type Documentation

Colorspaces for pixel data supported by Evas.

Enumerator
EVAS_COLORSPACE_ARGB8888 

ARGB 32 bits per pixel, high-byte is Alpha, accessed 1 32bit word at a time.

EVAS_COLORSPACE_YCBCR422P601_PL 

YCbCr 4:2:2 Planar, ITU.BT-601 specifications.

The data pointed to is just an array of row pointer, pointing to the Y rows, then the Cb, then Cr rows

EVAS_COLORSPACE_YCBCR422P709_PL 

YCbCr 4:2:2 Planar, ITU.BT-709 specifications.

The data pointed to is just an array of row pointer, pointing to the Y rows, then the Cb, then Cr rows

EVAS_COLORSPACE_RGB565_A5P 

16bit rgb565 + Alpha plane at end - 5 bits of the 8 being used per alpha byte

EVAS_COLORSPACE_GRY8 

8bit grayscale

EVAS_COLORSPACE_YCBCR422601_PL 

YCbCr 4:2:2, ITU.BT-601 specifications.

The data pointed to is just an array of row pointer, pointing to line of Y,Cb,Y,Cr bytes

EVAS_COLORSPACE_YCBCR420NV12601_PL 

YCbCr 4:2:0, ITU.BT-601 specification.

The data pointed to is just an array of row pointer, pointing to the Y rows, then the Cb,Cr rows.

EVAS_COLORSPACE_YCBCR420TM12601_PL 

YCbCr 4:2:0, ITU.BT-601 specification.

The data pointed to is just an array of tiled row pointer, pointing to the Y rows, then the Cb,Cr rows.

EVAS_COLORSPACE_AGRY88 

AY 8bits Alpha and 8bits Grey, accessed 1 16bits at a time.

EVAS_COLORSPACE_ETC1 

OpenGL ETC1 encoding of RGB texture (4 bit per pixel)

Since
1.10
EVAS_COLORSPACE_RGB8_ETC2 

OpenGL GL_COMPRESSED_RGB8_ETC2 texture compression format (4 bit per pixel)

Since
1.10
EVAS_COLORSPACE_RGBA8_ETC2_EAC 

OpenGL GL_COMPRESSED_RGBA8_ETC2_EAC texture compression format, supports alpha (8 bit per pixel)

Since
1.10
EVAS_COLORSPACE_ETC1_ALPHA 

ETC1 with alpha support using two planes: ETC1 RGB and ETC1 grey for alpha.

Since
1.11
EVAS_COLORSPACE_RGB_S3TC_DXT1 

OpenGL COMPRESSED_RGB_S3TC_DXT1_EXT format with RGB only.

Since
1.11
EVAS_COLORSPACE_RGBA_S3TC_DXT1 

OpenGL COMPRESSED_RGBA_S3TC_DXT1_EXT format with RGBA punchthrough.

Since
1.11
EVAS_COLORSPACE_RGBA_S3TC_DXT2 

DirectDraw DXT2 format with premultiplied RGBA.

Not supported by OpenGL itself.

Since
1.11
EVAS_COLORSPACE_RGBA_S3TC_DXT3 

OpenGL COMPRESSED_RGBA_S3TC_DXT3_EXT format with RGBA.

Since
1.11
EVAS_COLORSPACE_RGBA_S3TC_DXT4 

DirectDraw DXT4 format with premultiplied RGBA.

Not supported by OpenGL itself.

Since
1.11
EVAS_COLORSPACE_RGBA_S3TC_DXT5 

OpenGL COMPRESSED_RGBA_S3TC_DXT5_EXT format with RGBA.

Since
1.11

Function Documentation

Eina_Bool evas_object_image_extension_can_load_get ( const char *  file)

Check if a file extension may be supported by Image Object Functions.

Parameters
fileThe file to check
Returns
EINA_TRUE if we may be able to open it, EINA_FALSE if it's unlikely.
Since
1.1

If file is a Eina_Stringshare, use directly evas_object_image_extension_can_load_fast_get.

This functions is threadsafe.

References eina_stringshare_add(), and eina_stringshare_del().

Eina_Bool evas_object_image_extension_can_load_fast_get ( const char *  file)

Check if a file extension may be supported by Image Object Functions.

Parameters
fileThe file to check, it should be an Eina_Stringshare.
Returns
EINA_TRUE if we may be able to open it, EINA_FALSE if it's unlikely.
Since
1.1

This functions is threadsafe.

Evas_Object* evas_object_image_add ( Evas e)

Creates a new image object on the given Evas e canvas.

Parameters
eThe given canvas.
Returns
The created image object handle.
Note
If you intend to display an image somehow in a GUI, besides binding it to a real image file/source (with evas_object_image_file_set(), for example), you'll have to tell this image object how to fill its space with the pixels it can get from the source. See evas_object_image_filled_add(), for a helper on the common case of scaling up an image source to the whole area of the image object.
See also
evas_object_image_fill_set()

Example:

1 img = evas_object_image_add(canvas);
2 evas_object_image_file_set(img, "/path/to/img", NULL);

Referenced by ecore_evas_cursor_set(), ecore_evas_ews_new(), ecore_evas_object_image_new(), ethumb_dup(), ethumb_new(), and evas_object_image_filled_add().

Evas_Object* evas_object_image_filled_add ( Evas e)

Creates a new image object that automatically scales its bound image to the object's area, on both axis.

Parameters
eThe given canvas.
Returns
The created image object handle.

This is a helper function around evas_object_image_add() and evas_object_image_filled_set(). It has the same effect of applying those functions in sequence, which is a very common use case.

Note
Whenever this object gets resized, the bound image will be rescaled, too.
See also
evas_object_image_add()
evas_object_image_filled_set()
evas_object_image_fill_set()
Examples:
ecore_evas_buffer_example_02.c, edje-basic.c, edje-signals-messages.c, ephysics_logo.c, evas-aspect-hints.c, evas-box.c, evas-events.c, evas-hints.c, evas-images.c, evas-images2.c, evas-map-utils.c, evas-object-manipulation.c, evas-smart-interface.c, evas-smart-object.c, and evas-text.c.

References evas_object_image_add().

void evas_object_image_memfile_set ( Evas_Object obj,
void *  data,
int  size,
char *  format,
char *  key 
)

Sets the data for an image from memory to be loaded.

This is the same as evas_object_image_file_set() but the file to be loaded may exist at an address in memory (the data for the file, not the filename itself). The data at the address is copied and stored for future use, so no data needs to be kept after this call is made. It will be managed and freed for you when no longer needed. The size is limited to 2 gigabytes in size, and must be greater than 0. A NULL data pointer is also invalid. Set the filename to NULL to reset to empty state and have the image file data freed from memory using evas_object_image_file_set().

The format is optional (pass NULL if you don't need/use it). It is used to help Evas guess better which loader to use for the data. It may simply be the "extension" of the file as it would normally be on disk such as "jpg" or "png" or "gif" etc.

Parameters
objThe given image object.
dataThe image file data address
sizeThe size of the image file data in bytes
formatThe format of the file (optional), or NULL if not needed
keyThe image key in file, or NULL.

References eina_file_close(), eina_file_virtualize(), and EINA_TRUE.

void evas_object_image_native_surface_set ( Evas_Object obj,
Evas_Native_Surface surf 
)

Set the native surface of a given image of the canvas.

Parameters
objThe given canvas pointer.
surfThe new native surface.

This function sets a native surface of a given canvas image.

References EVAS_CALLBACK_DEL, evas_object_event_callback_add(), and evas_object_event_callback_del_full().

void evas_object_image_preload ( Evas_Object obj,
Eina_Bool  cancel 
)

Preload an image object's image data in the background.

Parameters
objThe given image object.
cancelEINA_FALSE will add it the preloading work queue, EINA_TRUE will remove it (if it was issued before).

This function requests the preload of the data image in the background. The work is queued before being processed (because there might be other pending requests of this type).

Whenever the image data gets loaded, Evas will call EVAS_CALLBACK_IMAGE_PRELOADED registered callbacks on obj (what may be immediately, if the data was already preloaded before).

Use EINA_TRUE for cancel on scenarios where you don't need the image data preloaded anymore.

Note
Any evas_object_show() call after evas_object_image_preload() will make the latter to be cancelled, with the loading process now taking place synchronously (and, thus, blocking the return of the former until the image is loaded). It is highly advisable, then, that the user preload an image with it being hidden, just to be shown on the EVAS_CALLBACK_IMAGE_PRELOADED event's callback.
Examples:
evas-images2.c.
Eina_Bool evas_object_image_source_unset ( Evas_Object obj)

Clear the source object on a proxy image object.

Parameters
objImage object to clear source of.
Returns
EINA_TRUE on success, EINA_FALSE on error.

This is equivalent to calling evas_object_image_source_set() with a NULL source.

References EINA_FALSE.

void evas_object_image_alpha_mask_set ( Evas_Object obj,
Eina_Bool  ismask 
)

Enable an image to be used as an alpha mask.

This will set any flags, and discard any excess image data not used as an alpha mask.

Note there is little point in using a image as alpha mask unless it has an alpha channel.

Parameters
objObject to use as an alpha mask.
ismaskUse image as alphamask, must be true.
void evas_object_image_file_set ( Eo obj,
const char *  file,
const char *  key 
)

Set the source file from where an image object must fetch the real image data (it may be an Eet file, besides pure image ones).

If the file supports multiple data stored in it (as Eet files do), you can specify the key to be used as the index of the image in this file.

Example:

1 img = evas_object_image_add(canvas);
2 evas_object_image_file_set(img, "/path/to/img", NULL);
3 err = evas_object_image_load_error_get(img);
4 if (err != EVAS_LOAD_ERROR_NONE)
5 {
6 fprintf(stderr, "could not load image '%s'. error string is \"%s\"\n",
7 valid_path, evas_load_error_str(err));
8 }
9 else
10 {
11 evas_object_image_fill_set(img, 0, 0, w, h);
12 evas_object_resize(img, w, h);
13 evas_object_show(img);
14 }
Parameters
[in]fileThe image file path.
[in]keyThe image key in file (if its an Eet one), or NULL, otherwise.
Examples:
ecore_evas_buffer_example_02.c, edje-basic.c, edje-signals-messages.c, ephysics_logo.c, evas-aspect-hints.c, evas-box.c, evas-events.c, evas-hints.c, evas-images.c, evas-images2.c, evas-map-utils.c, evas-object-manipulation.c, evas-smart-interface.c, evas-smart-object.c, and evas-text.c.

Referenced by ecore_evas_cursor_set().

void evas_object_image_file_get ( const Eo obj,
const char **  file,
const char **  key 
)

Retrieve the source file from where an image object is to fetch the real image data (it may be an Eet file, besides pure image ones).

You must not modify the strings on the returned pointers.

Note
Use NULL pointers on the file components you're not interested in: they'll be ignored by the function.
Parameters
[out]fileThe image file path.
[out]keyThe image key in file (if its an Eet one), or NULL, otherwise.
Eina_Bool evas_object_image_save ( const Eo obj,
const char *  file,
const char *  key,
const char *  flags 
)

Save the given image object's contents to an (image) file.

The extension suffix on file will determine which saver module Evas is to use when saving, thus the final file's format. If the file supports multiple data stored in it (Eet ones), you can specify the key to be used as the index of the image in it.

You can specify some flags when saving the image. Currently acceptable flags are quality and compress. Eg.: "quality=100 compress=9"

Parameters
[in]fileThe filename to be used to save the image (extension obligatory).
[in]keyThe image key in the file (if an Eet one), or NULL, otherwise.
[in]flagsString containing the flags to be used (NULL for none).
Examples:
evas-images2.c.
Eina_Bool evas_object_image_animated_get ( const Eo obj)

Check if an image object can be animated (have multiple frames)

Returns
whether obj support animation

This returns if the image file of an image object is capable of animation such as an animated gif file might. This is only useful to be called once the image object file has been set.

Example:

1 extern Evas_Object *obj;
2 
3 if (evas_object_image_animated_get(obj))
4 {
5 int frame_count;
6 int loop_count;
7 Evas_Image_Animated_Loop_Hint loop_type;
8 double duration;
9 
10 frame_count = evas_object_image_animated_frame_count_get(obj);
11 printf("This image has %d frames\n",frame_count);
12 
13 duration = evas_object_image_animated_frame_duration_get(obj,1,0);
14 printf("Frame 1's duration is %f. You had better set object's frame to 2 after this duration using timer\n");
15 
16 loop_count = evas_object_image_animated_loop_count_get(obj);
17 printf("loop count is %d. You had better run loop %d times\n",loop_count,loop_count);
18 
19 loop_type = evas_object_image_animated_loop_type_get(obj);
20 if (loop_type == EVAS_IMAGE_ANIMATED_HINT_LOOP)
21 printf("You had better set frame like 1->2->3->1->2->3...\n");
22 else if (loop_type == EVAS_IMAGE_ANIMATED_HINT_PINGPONG)
23 printf("You had better set frame like 1->2->3->2->1->2...\n");
24 else
25 printf("Unknown loop type\n");
26 
27 evas_object_image_animated_frame_set(obj,1);
28 printf("You set image object's frame to 1. You can see frame 1\n");
29 }
See also
evas_object_image_animated_get()
evas_object_image_animated_frame_count_get()
evas_object_image_animated_loop_type_get()
evas_object_image_animated_loop_count_get()
evas_object_image_animated_frame_duration_get()
evas_object_image_animated_frame_set()
Since
1.1
void evas_object_image_load_size_set ( Eo obj,
int  w,
int  h 
)

Set the load size of a given image object's source image.

This function sets a new geometry size for the given canvas image. The image will be loaded into memory as if it was the set size instead of the original size.

Note
The size of a given image object's source image will be less than or equal to the size of w and h.
See also
evas_object_image_load_size_get()
Parameters
[in]wThe new width of the image's load size.
[in]hThe new height of the image's load size.
void evas_object_image_load_size_get ( const Eo obj,
int *  w,
int *  h 
)

Get the load size of a given image object's source image.

This function gets the geometry size set manually for the given canvas image.

Note
Use NULL pointers on the size components you're not interested in: they'll be ignored by the function.
w and h will be set with the image's loading size only if the image's load size is set manually: if evas_object_image_load_size_set() has not been called, w and h will be set with 0.
See also
evas_object_image_load_size_set() for more details
Parameters
[out]wThe new width of the image's load size.
[out]hThe new height of the image's load size.
void evas_object_image_smooth_scale_set ( Eo obj,
Eina_Bool  smooth_scale 
)

Sets whether to use high-quality image scaling algorithm on the given image object.

When enabled, a higher quality image scaling algorithm is used when scaling images to sizes other than the source image's original one. This gives better results but is more computationally expensive.

Note
Image objects get created originally with smooth scaling on.
See also
evas_object_image_smooth_scale_get()
Parameters
[in]smooth_scaleWhether to use smooth scale or not.
Examples:
evas-images.c.
Eina_Bool evas_object_image_smooth_scale_get ( const Eo obj)

Retrieves whether the given image object is using high-quality image scaling algorithm.

Returns
Whether smooth scale is being used.

See evas_object_image_smooth_scale_set() for more details.

Examples:
evas-images.c.