From 8e5ff49ff73f51e9aa0226548059024a7a894254 Mon Sep 17 00:00:00 2001
From: sagudev <16504129+sagudev@users.noreply.github.com>
Date: Fri, 25 Oct 2024 07:41:12 +0200
Subject: [PATCH 1/2] add components_per_format, bytes_per_type

Signed-off-by: sagudev <16504129+sagudev@users.noreply.github.com>
---
 src/lib.rs | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/src/lib.rs b/src/lib.rs
index 50f1c37..3752ed4 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1803,6 +1803,32 @@ pub trait HasContext: __private::Sealed {
     unsafe fn max_shader_compiler_threads(&self, count: u32);
 }
 
+/// Returns number of components used by format
+pub fn components_per_format(format: u32) -> usize {
+    match format {
+        RED | GREEN | BLUE => 1,
+        RED_INTEGER | GREEN_INTEGER | BLUE_INTEGER => 1,
+        ALPHA | LUMINANCE | DEPTH_COMPONENT => 1,
+        RG | LUMINANCE_ALPHA => 2,
+        RGB | BGR => 3,
+        RGBA | BGRA => 4,
+        _ => panic!("unsupported format: {:?}", format),
+    }
+}
+
+/// Returns number of bytes used by pixel type (in one component)
+pub fn bytes_per_type(pixel_type: u32) -> usize {
+    // per https://www.khronos.org/opengl/wiki/Pixel_Transfer#Pixel_type
+    match pixel_type {
+        BYTE | UNSIGNED_BYTE => 1,
+        SHORT | UNSIGNED_SHORT => 2,
+        INT | UNSIGNED_INT => 4,
+        HALF_FLOAT | HALF_FLOAT_OES => 2,
+        FLOAT => 4,
+        _ => panic!("unsupported pixel type: {:?}", pixel_type),
+    }
+}
+
 pub const ACTIVE_ATOMIC_COUNTER_BUFFERS: u32 = 0x92D9;
 
 pub const ACTIVE_ATTRIBUTES: u32 = 0x8B89;

From 16bfeea395e47e3b391a34ded25b3b2758d234af Mon Sep 17 00:00:00 2001
From: sagudev <16504129+sagudev@users.noreply.github.com>
Date: Sun, 27 Oct 2024 19:13:37 +0100
Subject: [PATCH 2/2] Add compute_size

Signed-off-by: sagudev <16504129+sagudev@users.noreply.github.com>
---
 src/lib.rs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/lib.rs b/src/lib.rs
index 3752ed4..1e56627 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1829,6 +1829,10 @@ pub fn bytes_per_type(pixel_type: u32) -> usize {
     }
 }
 
+pub fn compute_size(width: i32, height: i32, format: u32, pixel_type: u32) -> usize {
+    width as usize * height as usize * components_per_format(format) * bytes_per_type(pixel_type)
+}
+
 pub const ACTIVE_ATOMIC_COUNTER_BUFFERS: u32 = 0x92D9;
 
 pub const ACTIVE_ATTRIBUTES: u32 = 0x8B89;