From ff7e64494fdb9452e59e73ca22a9676dc343880d Mon Sep 17 00:00:00 2001
From: Lynix <lynix680@gmail.com>
Date: Fri, 18 Nov 2016 01:15:58 +0100
Subject: [PATCH] Utility/Image: Add HasAlpha() method

---
 include/Nazara/Utility/Image.hpp |  2 ++
 src/Nazara/Utility/Image.cpp     | 38 ++++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+)

diff --git a/include/Nazara/Utility/Image.hpp b/include/Nazara/Utility/Image.hpp
index 029157885..e1712aed1 100644
--- a/include/Nazara/Utility/Image.hpp
+++ b/include/Nazara/Utility/Image.hpp
@@ -91,6 +91,8 @@ namespace Nz
 			ImageType GetType() const;
 			unsigned int GetWidth(UInt8 level = 0) const;
 
+			bool HasAlpha() const;
+
 			bool IsValid() const;
 
 			// Load
diff --git a/src/Nazara/Utility/Image.cpp b/src/Nazara/Utility/Image.cpp
index b4be2c7c5..39d99cdd1 100644
--- a/src/Nazara/Utility/Image.cpp
+++ b/src/Nazara/Utility/Image.cpp
@@ -825,6 +825,44 @@ namespace Nz
 		return GetLevelSize(m_sharedImage->width, level);
 	}
 
+	bool Image::HasAlpha() const
+	{
+		NazaraAssert(m_sharedImage != &emptyImage, "Image must be valid");
+
+		if (!PixelFormat::HasAlpha(m_sharedImage->format))
+			return false;
+
+		if (!PixelFormat::IsCompressed(m_sharedImage->format))
+		{
+			const PixelFormatInfo& info = PixelFormat::GetInfo(m_sharedImage->format);
+			const UInt8* pixel = GetConstPixels();
+
+			Bitset<> workingBitset;
+			std::size_t pixelCount = m_sharedImage->width * m_sharedImage->height * ((m_sharedImage->type == ImageType_Cubemap) ? 6 : m_sharedImage->depth);
+			if (pixelCount == 0)
+				return false;
+
+			auto seq = workingBitset.Read(GetConstPixels(), info.bitsPerPixel);
+			do
+			{
+				workingBitset &= info.alphaMask;
+				if (workingBitset.Count() != info.alphaMask.Count()) //< Means that at least one bit of the alpha mask of this pixel is disabled
+					return true;
+
+				workingBitset.Clear();
+				workingBitset.Read(seq, info.bitsPerPixel);
+			}
+			while (--pixelCount > 0);
+
+			return false;
+		}
+		else
+		{
+			// FIXME: Currently, we assume the pixel format is already the right one
+			return true;
+		}
+	}
+
 	bool Image::IsValid() const
 	{
 		return m_sharedImage != &emptyImage;