1 #ifndef DALI_TOOLKIT_ASYNC_IMAGE_LOADER_H
2 #define DALI_TOOLKIT_ASYNC_IMAGE_LOADER_H
5 * Copyright (c) 2020 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.
21 #include <dali/public-api/images/image-operations.h>
22 #include <dali/public-api/object/base-handle.h>
23 #include <dali/public-api/signals/dali-signal.h>
27 #include <dali-toolkit/public-api/dali-toolkit-common.h>
35 namespace Internal DALI_INTERNAL
37 class AsyncImageLoader;
41 * @addtogroup dali_toolkit_image_loader
46 * @brief The AsyncImageLoader is used to load pixel data from a URL asynchronously.
48 * The images are loaded in a worker thread to avoid blocking the main event thread.
50 * To keep track of the loading images, each load call is assigned an ID (which is returned by the Load() call).
51 * To know when the Load has completed, connect to the ImageLoadedSignal.
52 * This signal should be connected before Load is called (in case the signal is emitted immediately).
54 * Load errors can be detected by checking the PixelData object is valid from within the signal handler.
56 * Note: The PixelData object will automatically be destroyed when it leaves its scope.
61 * class MyClass : public ConnectionTracker
65 * MyCallback( uint32_t loadedTaskId, PixelData pixelData )
67 * // First check if the image loaded correctly.
70 * if( loadedTaskId == mId1 )
72 * // use the loaded pixel data from the first image
74 * else if( loadedTaskId == mId2 )
76 * // use the loaded pixel data from the second image
86 * AsyncImageLoader imageLoader = AsyncImageLoader::New();
88 * // Connect the signal here.
89 * imageLoader.ImageLoadedSignal().Connect( &myObject, &MyClass::MyCallback );
91 * // Invoke the load calls (must do this after connecting the signal to guarantee callbacks occur).
92 * myObject.mId1 = imageLoader.Load( "first_image_url.jpg" );
93 * myObject.mId2 = imageLoader.Load( "second_image_url.jpg" );
97 class DALI_TOOLKIT_API AsyncImageLoader : public BaseHandle
100 typedef Signal<void(uint32_t, PixelData)> ImageLoadedSignalType; ///< Image loaded signal type @SINCE_1_2_14
104 * @brief Constructor which creates an empty AsyncImageLoader handle.
107 * Use AsyncImageLoader::New() to create an initialised object.
115 * This is non-virtual since derived Handle types must not contain data or virtual methods.
120 * @brief This copy constructor is required for (smart) pointer semantics.
123 * @param[in] handle A reference to the copied handle
125 AsyncImageLoader(const AsyncImageLoader& handle);
128 * @brief Move constructor
131 * @param[in] rhs A reference to the moved handle
133 AsyncImageLoader(AsyncImageLoader&& rhs);
136 * @brief This assignment operator is required for (smart) pointer semantics.
139 * @param[in] handle A reference to the copied handle
140 * @return A reference to this
142 AsyncImageLoader& operator=(const AsyncImageLoader& handle);
145 * @brief Move assignment
148 * @param[in] rhs A reference to the moved handle
150 AsyncImageLoader& operator=(AsyncImageLoader&& rhs);
153 * @brief Creates a new loader to load the image asynchronously in a worker thread.
156 * @return The image loader
158 static AsyncImageLoader New();
161 * @brief Downcasts a handle to AsyncImageLoader handle.
163 * If the handle points to an AsyncImageLoader object, the downcast produces a valid handle.
164 * If not, the returned handle is left uninitialized.
167 * @param[in] handle A handle to an object
168 * @return A handle to a AsyncImageLoader object or an uninitialized handle
170 static AsyncImageLoader DownCast(BaseHandle handle);
173 * @brief Starts an image loading task.
174 * Note: When using this method, the following defaults will be used:
175 * fittingMode = FittingMode::DEFAULT
176 * samplingMode = SamplingMode::BOX_THEN_LINEAR
177 * orientationCorrection = true
182 * @param[in] url The URL of the image file to load
183 * @return The loading task id
185 uint32_t Load(const std::string& url);
188 * @brief Starts an image loading task.
189 * Note: When using this method, the following defaults will be used:
190 * fittingMode = FittingMode::DEFAULT
191 * samplingMode = SamplingMode::BOX_THEN_LINEAR
192 * orientationCorrection = true
197 * @param[in] url The URL of the image file to load
198 * @param[in] dimensions The width and height to fit the loaded image to
199 * @return The loading task id
201 uint32_t Load(const std::string& url, ImageDimensions dimensions);
204 * @brief Starts an image loading task.
208 * @param[in] url The URL of the image file to load
209 * @param[in] dimensions The width and height to fit the loaded image to
210 * @param[in] fittingMode The method used to fit the shape of the image before loading to the shape defined by the size parameter
211 * @param[in] samplingMode The filtering method used when sampling pixels from the input image while fitting it to desired size
212 * @param[in] orientationCorrection Reorient the image to respect any orientation metadata in its header
213 * @return The loading task id
215 uint32_t Load(const std::string& url,
216 ImageDimensions dimensions,
217 FittingMode::Type fittingMode,
218 SamplingMode::Type samplingMode,
219 bool orientationCorrection);
222 * @brief Cancels an image loading task if it is still queueing in the work thread.
225 * @param[in] loadingTaskId The task id returned when invoking the load call.
226 * @return If true, the loading task is removed from the queue, otherwise the loading is already implemented and unable to cancel anymore
228 bool Cancel(uint32_t loadingTaskId);
231 * @brief Cancels all the loading tasks in the queue.
237 * @brief Signal emitted for connected callback functions to get access to the loaded pixel data.
239 * A callback of the following type may be connected:
241 * void YourCallbackName( uint32_t id, PixelData pixelData );
244 * @return A reference to a signal object to Connect() with
246 ImageLoadedSignalType& ImageLoadedSignal();
248 public: // Not intended for developer use
251 * @brief Allows the creation of a AsyncImageLoader handle from an internal pointer.
253 * @note Not intended for application developers
255 * @param[in] impl A pointer to the object
257 explicit DALI_INTERNAL AsyncImageLoader(Internal::AsyncImageLoader* impl);
264 } // namespace Toolkit
268 #endif // DALI_TOOLKIT_ASYNC_IMAGE_LOADER_H