main : erase image example, mouse drag changes the underlying dynamic…

… texture data

drawing/erase_image.py

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+import dearpygui.dearpygui as dpg
+from math import sqrt
+dpg.create_context()
+
+CANVAS_WIDTH = 300
+CANVAS_HEIGHT = 300
+ERASE_COLOUR = (0,0,0,0)
+
+width, height, channels, data = dpg.load_image("beach.jpg")
+with dpg.texture_registry():
+    dpg.add_dynamic_texture(width, height, data, tag="beach")
+
+with dpg.theme() as canvas_theme, dpg.theme_component():
+    dpg.add_theme_style(dpg.mvStyleVar_WindowPadding, 0,0)
+
+def erase():
+    image_data = dpg.get_value("beach")
+    radius = dpg.get_value(circle_thickness)
+    while dpg.is_mouse_button_down(button=dpg.mvMouseButton_Left):
+        mouse_x,mouse_y = dpg.get_mouse_pos()
+        x = int(mouse_x/CANVAS_WIDTH * width)
+        y = int(mouse_y/CANVAS_HEIGHT * height)
+
+        for i in range(width):
+            for j in range(height):
+                distance = sqrt(((i / width) - (x / width))**2 + ((j / height) - (y / height))**2)
+                if distance <= radius / max(width, height):
+                    index = (j * width + i) * 4
+                    image_data[index] = ERASE_COLOUR[0]
+                    image_data[index + 1] = ERASE_COLOUR[1]
+                    image_data[index + 2] = ERASE_COLOUR[2]
+                    image_data[index + 3] = ERASE_COLOUR[3]
+
+        dpg.set_value("beach", image_data)
+
+
+def reset_image():
+    dpg.set_value("beach", data)
+
+with dpg.window() as window:
+    dpg.add_text("Click and drag to erase.")
+    with dpg.group(horizontal=True):
+
+        with dpg.child_window(width=CANVAS_WIDTH, height=CANVAS_HEIGHT) as canvas:
+            dpg.bind_item_theme(canvas, canvas_theme)
+
+            with dpg.drawlist(width=CANVAS_WIDTH, height=CANVAS_HEIGHT) as drawlist:
+                dpg.draw_image(texture_tag="beach", pmin=(0,0), pmax=(CANVAS_WIDTH,CANVAS_HEIGHT))
+
+            with dpg.item_handler_registry() as registry:
+                dpg.add_item_clicked_handler(button=dpg.mvMouseButton_Left, callback=erase)
+            dpg.bind_item_handler_registry(drawlist, registry)
+
+        with dpg.child_window(border=False):
+            circle_thickness = dpg.add_slider_int(label="Circle Thickness", width=200, default_value=10, min_value=1, max_value=30)
+            dpg.add_button(label="Reset image", callback=reset_image)
+
+
+dpg.set_primary_window(window, True)
+dpg.create_viewport(width=900, height=600, title="Erase image")
+dpg.setup_dearpygui()
+dpg.show_viewport()
+dpg.start_dearpygui()
+dpg.destroy_context()