From 5de76c05a3929004caacb1eb55b9a48fad99001c Mon Sep 17 00:00:00 2001
From: NPatch <npatsiouras@gmail.com>
Date: Sat, 16 May 2020 18:08:21 +0300
Subject: [PATCH] LodePNG and EXR parsers now set ImageContainer.m_hasAlpha.

hasAlpha field added in bimg::TextureInfo and bimg::imageGetSize.
---
 include/bimg/bimg.h  |  2 ++
 src/image.cpp        |  3 +-
 src/image_decode.cpp | 77 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 81 insertions(+), 1 deletion(-)

diff --git a/include/bimg/bimg.h b/include/bimg/bimg.h
index 7fe8a75..ef3a744 100644
--- a/include/bimg/bimg.h
+++ b/include/bimg/bimg.h
@@ -174,6 +174,7 @@ namespace bimg
 		uint8_t numMips;            //!< Number of MIP maps.
 		uint8_t bitsPerPixel;       //!< Format bits per pixel.
 		bool    cubeMap;            //!< Texture is cubemap.
+		bool	hasAlpha;			//!< Texture utilizes alpha channel.
 	};
 
 	struct ImageContainer
@@ -273,6 +274,7 @@ namespace bimg
 		, bool _hasMips
 		, uint16_t _numLayers
 		, TextureFormat::Enum _format
+		, bool _hasAlpha = false
 		);
 
 	///
diff --git a/src/image.cpp b/src/image.cpp
index f9f0b89..b39cf00 100644
--- a/src/image.cpp
+++ b/src/image.cpp
@@ -294,7 +294,7 @@ namespace bimg
 		return numMips;
 	}
 
-	uint32_t imageGetSize(TextureInfo* _info, uint16_t _width, uint16_t _height, uint16_t _depth, bool _cubeMap, bool _hasMips, uint16_t _numLayers, TextureFormat::Enum _format)
+	uint32_t imageGetSize(TextureInfo* _info, uint16_t _width, uint16_t _height, uint16_t _depth, bool _cubeMap, bool _hasMips, uint16_t _numLayers, TextureFormat::Enum _format, bool _hasAlpha)
 	{
 		const ImageBlockInfo& blockInfo = getBlockInfo(_format);
 		const uint8_t  bpp         = blockInfo.bitsPerPixel;
@@ -341,6 +341,7 @@ namespace bimg
 			_info->cubeMap   = _cubeMap;
 			_info->storageSize  = size;
 			_info->bitsPerPixel = bpp;
+			_info->hasAlpha = _hasAlpha;
 		}
 
 		return size;
diff --git a/src/image_decode.cpp b/src/image_decode.cpp
index 3e4ebe6..75ab35d 100644
--- a/src/image_decode.cpp
+++ b/src/image_decode.cpp
@@ -303,6 +303,75 @@ namespace bimg
 						bx::memCopy( (uint8_t*)output->m_data + ii*4, state.info_raw.palette + data[ii]*4, 4);
 					}
 				}
+
+				switch (state.info_raw.colortype) //Check for alpha values
+				{
+					case LCT_GREY:
+					case LCT_RGB:
+						break;
+
+					case LCT_GREY_ALPHA:
+						if (8 == state.info_raw.bitdepth)
+						{
+							for (uint32_t ii = 0, num = width * height; ii < num; ++ii)
+							{
+								const uint8_t* rgba = (uint8_t*)data + ii * 2;
+								bool has_alpha = rgba[1] < UINT8_MAX;
+								if (has_alpha)
+								{
+									output->m_hasAlpha = has_alpha;
+									break;
+								}
+							}
+						}
+						else if(16 == state.info_raw.bitdepth)
+						{
+							for (uint32_t ii = 0, num = width * height; ii < num; ++ii)
+							{
+								const uint16_t* rgba = (uint16_t*)data + ii * 2;
+								bool has_alpha = rgba[1] < UINT16_MAX;
+								if (has_alpha)
+								{
+									output->m_hasAlpha = has_alpha;
+									break;
+								}
+							}
+						}
+						break;
+
+					case LCT_RGBA:
+						if (8 == state.info_raw.bitdepth)
+						{
+							for (uint32_t ii = 0, num = width * height; ii < num; ++ii)
+							{
+								const uint8_t* dst = (uint8_t*)output->m_data + ii * 4;
+								bool has_alpha = dst[3] < UINT8_MAX;
+								if (has_alpha)
+								{
+									output->m_hasAlpha = has_alpha;
+									break;
+								}
+							}
+						}
+						else if (16 == state.info_raw.bitdepth)
+						{
+							for (uint32_t ii = 0, num = width * height; ii < num; ++ii)
+							{
+								const uint16_t* dst = (uint16_t*)output->m_data + ii * 4;
+								bool has_alpha = dst[3] < UINT16_MAX;
+								if (has_alpha)
+								{
+									output->m_hasAlpha = has_alpha;
+									break;
+								}
+							}
+						}
+						break;
+
+					case LCT_PALETTE:
+						output->m_hasAlpha = lodepng_has_palette_alpha(&state.info_raw);
+						break;
+				}
 			}
 			else
 			{
@@ -331,6 +400,8 @@ namespace bimg
 		uint32_t width  = 0;
 		uint32_t height = 0;
 
+		bool hasAlpha = false;
+
 		uint8_t* data = NULL;
 		const char* err = NULL;
 		EXRHeader exrHeader;
@@ -431,6 +502,8 @@ namespace bimg
 							};
 							bx::memCopy(&data[ii * bytesPerPixel], rgba, bytesPerPixel);
 
+							hasAlpha |= (hasAlpha || rgba[3] < 1.0f);
+
 							srcR += stepR;
 							srcG += stepG;
 							srcB += stepB;
@@ -457,6 +530,8 @@ namespace bimg
 							};
 							bx::memCopy(&data[ii * bytesPerPixel], rgba, bytesPerPixel);
 
+							hasAlpha |= (hasAlpha || rgba[3] < UINT16_MAX);
+
 							srcR += stepR;
 							srcG += stepG;
 							srcB += stepB;
@@ -512,8 +587,10 @@ namespace bimg
 				, data
 				);
 			BX_FREE(_allocator, data);
+			output->m_hasAlpha = hasAlpha;
 		}
 
+
 		return output;
 	}