1 #ifndef DALI_TOOLKIT_ASYNC_IMAGE_LOADER_H
2 #define DALI_TOOLKIT_ASYNC_IMAGE_LOADER_H
5 * Copyright (c) 2016 Samsung Electronics Co., Ltd.
7 * Licensed under the Apache License, Version 2.0 (the "License");
8 * you may not use this file except in compliance with the License.
9 * You may obtain a copy of the License at
11 * http://www.apache.org/licenses/LICENSE-2.0
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS,
15 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
22 #include <dali/public-api/object/base-handle.h>
23 #include <dali/public-api/images/image-operations.h>
24 #include <dali/public-api/signals/dali-signal.h>
33 namespace Internal DALI_INTERNAL
35 class AsyncImageLoader;
39 * @brief The AsyncImageLoader is used to load pixel data from a URL asynchronously.
41 * The images are loaded in a worker thread to avoid blocking the main event thread.
43 * To keep track of the loading images, each load call is assigned an ID (which is returned by the Load() call).
44 * To know when the Load has completed, connect to the ImageLoadedSignal.
45 * This signal should be connected before Load is called (in case the signal is emitted immediately).
47 * Load errors can be detected by checking the PixelData object is valid from within the signal handler.
49 * Note: The PixelData object will automatically be destroyed when it leaves its scope.
54 * class MyClass : public ConnectionTracker
58 * MyCallback( uint32_t loadedTaskId, PixelData pixelData )
60 * // First check if the image loaded correctly.
63 * if( loadedTaskId == mId1 )
65 * // use the loaded pixel data from the first image
67 * else if( loadedTaskId == mId2 )
69 * // use the loaded pixel data from the second image
79 * AsyncImageLoader imageLoader = AsyncImageLoader::New();
81 * // Connect the signal here.
82 * imageLoader.ImageLoadedSignal().Connect( &myObject, &MyClass::MyCallback );
84 * // Invoke the load calls (must do this after connecting the signal to guarantee callbacks occur).
85 * myObject.mId1 = imageLoader.Load( "first_image_url.jpg" );
86 * myObject.mId2 = imageLoader.Load( "second_image_url.jpg" );
90 class DALI_IMPORT_API AsyncImageLoader : public BaseHandle
94 typedef Signal< void( uint32_t, PixelData ) > ImageLoadedSignalType; ///< Image loaded signal type @SINCE_1_2_14
99 * @brief Constructor which creates an empty AsyncImageLoader handle.
102 * Use AsyncImageLoader::New() to create an initialised object.
110 * This is non-virtual since derived Handle types must not contain data or virtual methods.
115 * @brief This copy constructor is required for (smart) pointer semantics.
118 * @param[in] handle A reference to the copied handle
120 AsyncImageLoader( const AsyncImageLoader& handle );
123 * @brief This assignment operator is required for (smart) pointer semantics.
126 * @param[in] handle A reference to the copied handle
127 * @return A reference to this
129 AsyncImageLoader& operator=( const AsyncImageLoader& handle );
132 * @brief Creates a new loader to load the image asynchronously in a worker thread.
135 * @return The image loader
137 static AsyncImageLoader New();
140 * @brief Downcasts a handle to AsyncImageLoader handle.
142 * If the handle points to an AsyncImageLoader object, the downcast produces a valid handle.
143 * If not, the returned handle is left uninitialized.
146 * @param[in] handle A handle to an object
147 * @return A handle to a AsyncImageLoader object or an uninitialized handle
149 static AsyncImageLoader DownCast( BaseHandle handle );
152 * @brief Starts an image loading task.
153 * Note: When using this method, the following defaults will be used:
154 * fittingMode = FittingMode::DEFAULT
155 * samplingMode = SamplingMode::BOX_THEN_LINEAR
156 * orientationCorrection = true
161 * @param[in] url The URL of the image file to load
162 * @return The loading task id
164 uint32_t Load( const std::string& url );
167 * @brief Starts an image loading task.
168 * Note: When using this method, the following defaults will be used:
169 * fittingMode = FittingMode::DEFAULT
170 * samplingMode = SamplingMode::BOX_THEN_LINEAR
171 * orientationCorrection = true
176 * @param[in] url The URL of the image file to load
177 * @param[in] dimensions The width and height to fit the loaded image to
178 * @return The loading task id
180 uint32_t Load( const std::string& url, ImageDimensions dimensions );
183 * @brief Starts an image loading task.
187 * @param[in] url The URL of the image file to load
188 * @param[in] dimensions The width and height to fit the loaded image to
189 * @param[in] fittingMode The method used to fit the shape of the image before loading to the shape defined by the size parameter
190 * @param[in] samplingMode The filtering method used when sampling pixels from the input image while fitting it to desired size
191 * @param[in] orientationCorrection Reorient the image to respect any orientation metadata in its header
192 * @return The loading task id
194 uint32_t Load( const std::string& url,
195 ImageDimensions dimensions,
196 FittingMode::Type fittingMode,
197 SamplingMode::Type samplingMode,
198 bool orientationCorrection );
201 * @brief Cancels an image loading task if it is still queueing in the work thread.
204 * @param[in] loadingTaskId The task id returned when invoking the load call.
205 * @return If true, the loading task is removed from the queue, otherwise the loading is already implemented and unable to cancel anymore
207 bool Cancel( uint32_t loadingTaskId );
210 * @brief Cancels all the loading tasks in the queue.
216 * @brief Signal emitted for connected callback functions to get access to the loaded pixel data.
218 * A callback of the following type may be connected:
220 * void YourCallbackName( uint32_t id, PixelData pixelData );
223 * @return A reference to a signal object to Connect() with
225 ImageLoadedSignalType& ImageLoadedSignal();
227 public: // Not intended for developer use
231 * @brief Allows the creation of a AsyncImageLoader handle from an internal pointer.
233 * @note Not intended for application developers
235 * @param[in] impl A pointer to the object
237 explicit DALI_INTERNAL AsyncImageLoader( Internal::AsyncImageLoader* impl );
242 } // namespace Toolkit
246 #endif // DALI_TOOLKIT_ASYNC_IMAGE_LOADER_H