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Readme, Wiki: Image loading examples.

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docs/README.md
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@ -244,13 +244,13 @@ See the [Quotes](https://github.com/ocornut/imgui/wiki/Quotes) and [Software usi
The library started its life as "ImGui" due to the fact that I didn't give it a proper name when I released 1.0 and had no particular expectation that it would take off. However, the term IMGUI (immediate-mode graphical user interface) was coined before and is being used in variety of other situations (e.g. Unity uses it own implementation of the IMGUI paradigm). To reduce this ambiguity without affecting existing codebases, I have decided on an alternate, longer name "Dear ImGui" that people can use to refer to this specific library. Please try to refer to this library as "Dear ImGui".
**How can I tell whether to dispatch mouse/keyboard to Dear ImGui or to my application?**
<br>**How can I display an image? What is ImTextureID, how does it works?**
<br>**How can I display an image? What is ImTextureID, how does it works?** ([examples](https://github.com/ocornut/imgui/wiki/Image-Loading-and-Displaying-Examples))
<br>**Why are multiple widgets reacting when I interact with a single one? How can I have multiple widgets with the same label or with an empty label? A primer on labels and the ID Stack...**
<br>**How can I use my own math types instead of ImVec2/ImVec4?**
<br>**How can I load a different font than the default?**
<br>**How can I easily use icons in my application?**
<br>**How can I load multiple fonts?**
<br>**How can I display and input non-latin characters such as Chinese, Japanese, Korean, Cyrillic?** ([example](https://github.com/ocornut/imgui/wiki/Loading-Font-Example))
<br>**How can I display and input non-latin characters such as Chinese, Japanese, Korean, Cyrillic?** ([examples](https://github.com/ocornut/imgui/wiki/Loading-Font-Example))
<br>**How can I interact with standard C++ types (such as std::string and std::vector)?**
<br>**How can I use the drawing facilities without a Dear ImGui window? (using ImDrawList API)**
<br>**How can I use this without a mouse, without a keyboard or without a screen? (gamepad, input share, remote display)**

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docs/TODO.txt
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@ -93,6 +93,7 @@ It's mostly a bunch of personal notes, probably incomplete. Feel free to query i
- input text: a side bar that could e.g. preview where errors are. probably left to the user to draw but we'd need to give them the info there.
- input text: a way for the user to provide syntax coloring.
- input text: Shift+TAB with ImGuiInputTextFlags_AllowTabInput could eat preceding blanks, up to tab_count.
- input text: facilitate patterns like if (InputText(..., obj.get_string_ref()) { obj.set_string(...); } relying on internally held buffer.
- input text multi-line: don't directly call AddText() which does an unnecessary vertex reserve for character count prior to clipping. and/or more line-based clipping to AddText(). and/or reorganize TextUnformatted/RenderText for more efficiency for large text (e.g TextUnformatted could clip and log separately, etc).
- input text multi-line: support for cut/paste without selection (cut/paste the current line)
- input text multi-line: line numbers? status bar? (follow up on #200)
@ -111,6 +112,9 @@ It's mostly a bunch of personal notes, probably incomplete. Feel free to query i
- layout: more generic alignment state (left/right/centered) for single items?
- layout: clean up the InputFloatN/SliderFloatN/ColorEdit4 layout code. item width should include frame padding.
- layout: vertical alignment of mixed height items (e.g. buttons) within a same line (#1284)
- layout: null layout mode were items are not rendered but user can query GetItemRectMin()/Max/Size.
- layout: (R&D) local multi-pass layout mode.
- layout: (R&D) bind authored layout data (created by an off-line tool), items fetch their pos/size at submission, self-optimize data structures to stable linear access.
- group: BeginGroup() needs a border option. (~#1496)
- group: IsHovered() after EndGroup() covers whole aabb rather than the intersection of individual items. Is that desirable?

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imgui.cpp
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@ -622,6 +622,7 @@ CODE
Q: How can I display an image? What is ImTextureID, how does it works?
A: Short explanation:
- Please read Wiki entry for examples: https://github.com/ocornut/imgui/wiki/Image-Loading-and-Displaying-Examples
- You may use functions such as ImGui::Image(), ImGui::ImageButton() or lower-level ImDrawList::AddImage() to emit draw calls that will use your own textures.
- Actual textures are identified in a way that is up to the user/engine. Those identifiers are stored and passed as ImTextureID (void*) value.
- Loading image files from the disk and turning them into a texture is not within the scope of Dear ImGui (for a good reason).
@ -669,26 +670,9 @@ CODE
This is by design and is actually a good thing, because it means your code has full control over your data types and how you display them.
If you want to display an image file (e.g. PNG file) into the screen, please refer to documentation and tutorials for the graphics API you are using.
Here's a simplified OpenGL example using stb_image.h:
Refer to the Wiki to find simplified examples for loading textures with OpenGL, DirectX9 and DirectX11:
// Use stb_image.h to load a PNG from disk and turn it into raw RGBA pixel data:
#define STB_IMAGE_IMPLEMENTATION
#include <stb_image.h>
[...]
int my_image_width, my_image_height;
unsigned char* my_image_data = stbi_load("my_image.png", &my_image_width, &my_image_height, NULL, 4);
// Turn the RGBA pixel data into an OpenGL texture:
GLuint my_opengl_texture;
glGenTextures(1, &my_opengl_texture);
glBindTexture(GL_TEXTURE_2D, my_opengl_texture);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, image_width, image_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, image_data);
// Now that we have an OpenGL texture, assuming our imgui rendering function (imgui_impl_xxx.cpp file) takes GLuint as ImTextureID, we can display it:
ImGui::Image((void*)(intptr_t)my_opengl_texture, ImVec2(my_image_width, my_image_height));
https://github.com/ocornut/imgui/wiki/Image-Loading-and-Displaying-Examples
C/C++ tip: a void* is pointer-sized storage. You may safely store any pointer or integer into it by casting your value to ImTextureID / void*, and vice-versa.
Because both end-points (user code and rendering function) are under your control, you know exactly what is stored inside the ImTextureID / void*.