From 7e19b433cb08d473dc9ae3eb088f35fdd42962e2 Mon Sep 17 00:00:00 2001 From: omar Date: Wed, 8 Apr 2020 12:50:40 +0200 Subject: [PATCH] Updated Image Loading and Displaying Examples (markdown) --- Image-Loading-and-Displaying-Examples.md | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff --git a/Image-Loading-and-Displaying-Examples.md b/Image-Loading-and-Displaying-Examples.md index 4d7a98f..20a6197 100644 --- a/Image-Loading-and-Displaying-Examples.md +++ b/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. \ No newline at end of file +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)); +```