Navy.gif/imgui
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Updated Image Loading and Displaying Examples (markdown)

omar 2020-04-08 12:50:40 +02:00
parent c21c7847a5
commit 7e19b433cb
1 changed files with 15 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
Image-Loading-and-Displaying-Examples.md

@ -264,7 +264,7 @@ Finally, you may call `ImGui::ShowMetricsWindow()` to explore/visualize/understa
See e.g. http://wiki.polycount.com/wiki/Texture_Coordinates
The `ImGui::Image()` and `ImDrawList::AddImage()` functions allow you to pass "UV coordinates" corresponding to the upper-left and bottom-right portion of the texture you want to display. Using respectively `(0.0f, 0.0f)` and `(1.0f, 1.0f)` for those coordinates allow you to display the entire underlying texture. UV coordinates are traditionally normalized coordinates, meaning that for each axis, instead of counting a number of pixels in each axis, we address a location in the texture using a number from 0.0f to 1.0f. So (0.0f, 0.0f) is generally adressing the upper-left section of the texture and (1.0f, 1.0f) is addressing the lower-right corner of the texture.
The `ImGui::Image()` and `ImDrawList::AddImage()` functions allow you to pass "UV coordinates" corresponding to the upper-left and bottom-right portion of the texture you want to display. Using the default values, respectively `(0.0f, 0.0f)` and `(1.0f, 1.0f)` for those coordinates allow you to display the entire underlying texture. UV coordinates are traditionally normalized coordinates, meaning that for each axis, instead of counting a number of pixels in each axis, we address a location in the texture using a number from 0.0f to 1.0f. So (0.0f, 0.0f) is generally adressing the upper-left section of the texture and (1.0f, 1.0f) is addressing the lower-right corner of the texture.
If you want to display part of a texture, say display a 100x200 rectangle stored from pixel (10,10) to pixel (110,210) out of a 256x256 texture, you will need to calculate the normalized coordinates of those pixels:
@ -274,6 +274,19 @@ ImVec2 uv0 = ImVec2(10.0f/256.0f, 10.0f/256.0f);
// Normalized coordinates of pixel (110,210) in a 256x256 texture.
ImVec2 uv1 = ImVec2((10.0f+100.0f)/256.0f, (10.0f+200.0f)/256.0f);
// Display the 100x100 section starting at (10,10)
ImGui::Image((void*)texture, ImVec2(100.0f, 100.0f), uv0, uv1);
```
You can look up "texture coordinates" from other resources such as your favorite search engine, or graphics tutorials.
If you want to display the same image but scaled, keep the same UV coordinates but alter the Size:
```cpp
// Normal size
ImGui::Image((void*)texture, ImVec2(texture->Width, texture->Height), ImVec2(0.0f, 0.0f), ImVec2(1.0f, 1.0f));
// Half size, same contents
ImGui::Image((void*)texture, ImVec2(texture->Width*0.5f, texture->Height*0.5f), ImVec2(0.0f, 0.0f), ImVec2(1.0f, 1.0f));
```