feat(snapshot) add API to take snapshot for object (#2353)

* Fix image zooming causes unexpected object size.

Signed-off-by: Xu Xingliang <xuxingliang@xiaomi.com>

* add lv_snapshot_take API.

* fix(img) invalidate size and layout on zoom and angle change

* fix(img) not self-repeating under some zoom level.

* fix(snapshot) fix to keep the original position

* Move various set_px_cb_xx functions to lv_hal_disp.c

* add snapshot API to store image to provided buffer

* minor fixes and refactoring

* Move snapshot source to extra/others/snapshot.

1. Update parameter buff to buf.
2. Add macro to disable lv_snapshot, enabled by default.

* docs(others) add the others folder with snapshot.md

* docs(snapshot) added doc and example for snapshot.

1. Update doc snapshot.md
2. Add example lv_example_snapshot_1 to folder examples/others/snapshot
3. Update lv_conf_template.h and lv_conf_internal.h
4. Remove lv_snapshot.c from lv_misc.mk
5. Add others to index.md

Signed-off-by: Xu Xingliang <xuxingliang@xiaomi.com>

* add micropython example for snapshot

Co-authored-by: Xu Xingliang <xuxingliang@xiaomi.com>
Co-authored-by: Gabor Kiss-Vamosi <kisvegabor@gmail.com>

examples/lv_examples.h

@@ -23,6 +23,7 @@ extern "C" {
 #include "anim/lv_example_anim.h"
 #include "event/lv_example_event.h"
 #include "styles/lv_example_style.h"
+#include "others/lv_example_others.h"
 
 /*********************
  *      DEFINES

examples/others/lv_example_others.h

@@ -0,0 +1,37 @@
+/**
+ * @file lv_example_others.h
+ *
+ */
+
+#ifndef LV_EXAMPLE_OTHERS_H
+#define LV_EXAMPLE_OTHERS_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*********************
+ *      INCLUDES
+ *********************/
+#include "snapshot/lv_example_snapshot.h"
+/*********************
+ *      DEFINES
+ *********************/
+
+/**********************
+ *      TYPEDEFS
+ **********************/
+
+/**********************
+ * GLOBAL PROTOTYPES
+ **********************/
+
+/**********************
+ *      MACROS
+ **********************/
+
+#ifdef __cplusplus
+} /*extern "C"*/
+#endif
+
+#endif /*LV_EX_OTHERS_H*/

examples/others/snapshot/index.rst

@@ -0,0 +1,8 @@
+
+Simple snapshot example 
+"""""""""""""""""""
+
+.. lv_example:: others/snapshot/lv_example_snapshot_1
+  :language: c
+
+

examples/others/snapshot/lv_example_snapshot.h

@@ -0,0 +1,38 @@
+/**
+ * @file lv_example_snapshot.h
+ *
+ */
+
+#ifndef LV_EX_SNAPSHOT_H
+#define LV_EX_SNAPSHOT_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*********************
+ *      INCLUDES
+ *********************/
+
+/*********************
+ *      DEFINES
+ *********************/
+
+/**********************
+ *      TYPEDEFS
+ **********************/
+
+/**********************
+ * GLOBAL PROTOTYPES
+ **********************/
+void lv_example_snapshot_1(void);
+
+/**********************
+ *      MACROS
+ **********************/
+
+#ifdef __cplusplus
+} /*extern "C"*/
+#endif
+
+#endif /*LV_EX_GET_STARTED_H*/

examples/others/snapshot/lv_example_snapshot_1.c

@@ -0,0 +1,57 @@
+#include "../../lv_examples.h"
+#if LV_USE_SNAPSHOT && LV_BUILD_EXAMPLES
+
+static void event_cb(lv_event_t* e)
+{
+    lv_obj_t * snapshot_obj = lv_event_get_user_data(e);
+    lv_obj_t * img = lv_event_get_target(e);
+
+    if(snapshot_obj) {
+        lv_img_dsc_t* snapshot = (void*)lv_img_get_src(snapshot_obj);
+        if(snapshot){
+            lv_snapshot_free(snapshot);
+        }
+
+        /*Update the snapshot, we know parent of object is the container.*/
+        snapshot = lv_snapshot_take(img->parent, LV_IMG_CF_TRUE_COLOR_ALPHA);
+        if(snapshot == NULL)
+            return;
+        lv_img_set_src(snapshot_obj, snapshot);
+    }
+}
+
+void lv_example_snapshot_1(void)
+{
+    LV_IMG_DECLARE(img_star);
+    lv_obj_t * root = lv_scr_act();
+    lv_obj_set_style_bg_color(root, lv_palette_main(LV_PALETTE_LIGHT_BLUE), 0);
+
+    /*Create an image object to show snapshot*/
+    lv_obj_t * snapshot_obj = lv_img_create(root);
+    lv_obj_set_style_bg_color(snapshot_obj, lv_palette_main(LV_PALETTE_PURPLE), 0);
+    lv_obj_set_style_bg_opa(snapshot_obj, LV_OPA_100, 0);
+    lv_img_set_zoom(snapshot_obj, 128);
+
+    /*Create the container and its children*/
+    lv_obj_t * container = lv_obj_create(root);
+
+    lv_obj_align(container, LV_ALIGN_CENTER, 0, 0);
+    lv_obj_set_size(container, 180, 180);
+    lv_obj_set_flex_flow(container, LV_FLEX_FLOW_ROW_WRAP);
+    lv_obj_set_flex_align(container, LV_FLEX_ALIGN_SPACE_EVENLY, LV_FLEX_ALIGN_CENTER, LV_FLEX_ALIGN_CENTER);
+    lv_obj_set_style_radius(container, 50, 0);
+    lv_obj_t * img;
+    int i;
+    for(i = 0; i < 4; i++) {
+        img = lv_img_create(container);
+        lv_img_set_src(img, &img_star);
+        lv_obj_set_style_bg_color(img, lv_color_black(), 0);
+        lv_obj_set_style_bg_opa(img, LV_OPA_COVER, 0);
+        lv_obj_set_style_transform_zoom(img, 400, LV_STATE_PRESSED);
+        lv_obj_add_flag(img, LV_OBJ_FLAG_CLICKABLE);
+        lv_obj_add_event_cb(img, event_cb, LV_EVENT_PRESSED, snapshot_obj);
+        lv_obj_add_event_cb(img, event_cb, LV_EVENT_RELEASED, snapshot_obj);
+    }
+}
+
+#endif

examples/others/snapshot/lv_example_snapshot_1.py

@@ -0,0 +1,70 @@
+import lvgl as lv
+from imagetools import get_png_info, open_png
+
+# Register PNG image decoder
+decoder = lv.img.decoder_create()
+decoder.info_cb = get_png_info
+decoder.open_cb = open_png
+
+# Measure memory usage
+gc.enable()
+gc.collect()
+mem_free = gc.mem_free()
+
+label = lv.label(lv.scr_act())
+label.align(lv.ALIGN.BOTTOM_MID, 0, -10)
+label.set_text(" memory free:" + str(mem_free/1024) + " kB")
+
+# Create an image from the png file
+try:
+    with open('../../assets/img_star.png','rb') as f:
+        png_data = f.read()
+except:
+    print("Could not find img_star.png")
+    sys.exit()
+
+img_star = lv.img_dsc_t({
+  'data_size': len(png_data),
+  'data': png_data
+})
+
+def event_cb(e, snapshot_obj):
+    img = e.get_target()
+
+    if snapshot_obj:
+        # no need to free the old source for snapshot_obj, gc will free it for us.
+
+        # take a new snapshot, overwrite the old one
+        dsc = lv.snapshot_take(img.get_parent(), lv.img.CF.TRUE_COLOR_ALPHA)
+        snapshot_obj.set_src(dsc)
+
+    gc.collect()
+    mem_used = mem_free - gc.mem_free()
+    label.set_text("memory used:" + str(mem_used/1024) + " kB")
+
+root = lv.scr_act()
+root.set_style_bg_color(lv.palette_main(lv.PALETTE.LIGHT_BLUE), 0)
+
+# Create an image object to show snapshot
+snapshot_obj = lv.img(root)
+snapshot_obj.set_style_bg_color(lv.palette_main(lv.PALETTE.PURPLE), 0)
+snapshot_obj.set_style_bg_opa(lv.OPA.COVER, 0)
+snapshot_obj.set_zoom(128)
+
+# Create the container and its children
+container = lv.obj(root)
+container.align(lv.ALIGN.CENTER, 0, 0)
+container.set_size(180, 180)
+container.set_flex_flow(lv.FLEX_FLOW.ROW_WRAP)
+container.set_flex_align(lv.FLEX_ALIGN.SPACE_EVENLY, lv.FLEX_ALIGN.CENTER, lv.FLEX_ALIGN.CENTER)
+container.set_style_radius(50, 0)
+
+for i in range(4):
+    img = lv.img(container)
+    img.set_src(img_star)
+    img.set_style_bg_color(lv.palette_main(lv.PALETTE.GREY), 0)
+    img.set_style_bg_opa(lv.OPA.COVER, 0)
+    img.set_style_transform_zoom(400, lv.STATE.PRESSED)
+    img.add_flag(img.FLAG.CLICKABLE)
+    img.add_event_cb(lambda e: event_cb(e, snapshot_obj), lv.EVENT.PRESSED, None)
+    img.add_event_cb(lambda e: event_cb(e, snapshot_obj), lv.EVENT.RELEASED, None)