Add `etcpak` library for faster ETC/ETC2/S3TC imports.

- `etc` module was renamed to `etcpak` and modified to use the new library.
- PKM importer is removed in the process, it's obsolete.
- Old library `etc2comp` is removed.
- S3TC compression no longer done via `squish` (but decompression still is).
- Slight modifications to etcpak sources for MinGW compatibility,
  to fix LLVM `-Wc++11-narrowing` errors, and to allow using vendored or
  system libpng.

Co-authored-by: Rémi Verschelde <rverschelde@gmail.com>

13 files changed, 253 insertions, 544 deletions

diff --git a/modules/etc/SCsub b/modules/etc/SCsub
deleted file mode 100644
index 9b46f17916..0000000000
--- a/modules/etc/SCsub
+++ /dev/null
@@ -1,48 +0,0 @@
-#!/usr/bin/env python
-
-Import("env")
-Import("env_modules")
-
-env_etc = env_modules.Clone()
-
-# Thirdparty source files
-
-thirdparty_obj = []
-
-# Not unbundled so far since not widespread as shared library
-thirdparty_dir = "#thirdparty/etc2comp/"
-thirdparty_sources = [
-    "EtcBlock4x4.cpp",
-    "EtcBlock4x4Encoding.cpp",
-    "EtcBlock4x4Encoding_ETC1.cpp",
-    "EtcBlock4x4Encoding_R11.cpp",
-    "EtcBlock4x4Encoding_RG11.cpp",
-    "EtcBlock4x4Encoding_RGB8A1.cpp",
-    "EtcBlock4x4Encoding_RGB8.cpp",
-    "EtcBlock4x4Encoding_RGBA8.cpp",
-    "Etc.cpp",
-    "EtcDifferentialTrys.cpp",
-    "EtcFilter.cpp",
-    "EtcImage.cpp",
-    "EtcIndividualTrys.cpp",
-    "EtcMath.cpp",
-    "EtcSortedBlockList.cpp",
-]
-thirdparty_sources = [thirdparty_dir + file for file in thirdparty_sources]
-
-env_etc.Prepend(CPPPATH=[thirdparty_dir])
-
-env_thirdparty = env_etc.Clone()
-env_thirdparty.disable_warnings()
-env_thirdparty.add_source_files(thirdparty_obj, thirdparty_sources)
-env.modules_sources += thirdparty_obj
-
-# Godot source files
-
-module_obj = []
-
-env_etc.add_source_files(module_obj, "*.cpp")
-env.modules_sources += module_obj
-
-# Needed to force rebuilding the module files when the thirdparty library is updated.
-env.Depends(module_obj, thirdparty_obj)
diff --git a/modules/etc/image_compress_etc.cpp b/modules/etc/image_compress_etc.cpp
deleted file mode 100644
index 41cbbe3f54..0000000000
--- a/modules/etc/image_compress_etc.cpp
+++ /dev/null
@@ -1,226 +0,0 @@
-/*************************************************************************/
-/*  image_compress_etc.cpp                                               */
-/*************************************************************************/
-/*                       This file is part of:                           */
-/*                           GODOT ENGINE                                */
-/*                      https://godotengine.org                          */
-/*************************************************************************/
-/* Copyright (c) 2007-2021 Juan Linietsky, Ariel Manzur.                 */
-/* Copyright (c) 2014-2021 Godot Engine contributors (cf. AUTHORS.md).   */
-/*                                                                       */
-/* Permission is hereby granted, free of charge, to any person obtaining */
-/* a copy of this software and associated documentation files (the       */
-/* "Software"), to deal in the Software without restriction, including   */
-/* without limitation the rights to use, copy, modify, merge, publish,   */
-/* distribute, sublicense, and/or sell copies of the Software, and to    */
-/* permit persons to whom the Software is furnished to do so, subject to */
-/* the following conditions:                                             */
-/*                                                                       */
-/* The above copyright notice and this permission notice shall be        */
-/* included in all copies or substantial portions of the Software.       */
-/*                                                                       */
-/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
-/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
-/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
-/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
-/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
-/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
-/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
-/*************************************************************************/
-
-#include "image_compress_etc.h"
-
-#include "core/io/image.h"
-#include "core/os/copymem.h"
-#include "core/os/os.h"
-#include "core/string/print_string.h"
-
-#include <Etc.h>
-#include <EtcFilter.h>
-
-static Image::Format _get_etc2_mode(Image::UsedChannels format) {
-	switch (format) {
-		case Image::USED_CHANNELS_R:
-			return Image::FORMAT_ETC2_R11;
-
-		case Image::USED_CHANNELS_RG:
-			return Image::FORMAT_ETC2_RG11;
-
-		case Image::USED_CHANNELS_RGB:
-			return Image::FORMAT_ETC2_RGB8;
-
-		case Image::USED_CHANNELS_RGBA:
-			return Image::FORMAT_ETC2_RGBA8;
-
-		// TODO: would be nice if we could use FORMAT_ETC2_RGB8A1 for FORMAT_RGBA5551
-		default:
-			// TODO: Kept for compatibility, but should be investigated whether it's correct or if it should error out
-			return Image::FORMAT_ETC2_RGBA8;
-	}
-}
-
-static Etc::Image::Format _image_format_to_etc2comp_format(Image::Format format) {
-	switch (format) {
-		case Image::FORMAT_ETC:
-			return Etc::Image::Format::ETC1;
-
-		case Image::FORMAT_ETC2_R11:
-			return Etc::Image::Format::R11;
-
-		case Image::FORMAT_ETC2_R11S:
-			return Etc::Image::Format::SIGNED_R11;
-
-		case Image::FORMAT_ETC2_RG11:
-			return Etc::Image::Format::RG11;
-
-		case Image::FORMAT_ETC2_RG11S:
-			return Etc::Image::Format::SIGNED_RG11;
-
-		case Image::FORMAT_ETC2_RGB8:
-			return Etc::Image::Format::RGB8;
-
-		case Image::FORMAT_ETC2_RGBA8:
-			return Etc::Image::Format::RGBA8;
-
-		case Image::FORMAT_ETC2_RGB8A1:
-			return Etc::Image::Format::RGB8A1;
-
-		default:
-			ERR_FAIL_V(Etc::Image::Format::UNKNOWN);
-	}
-}
-
-static void _compress_etc(Image *p_img, float p_lossy_quality, bool force_etc1_format, Image::UsedChannels p_channels) {
-	Image::Format img_format = p_img->get_format();
-
-	if (img_format >= Image::FORMAT_DXT1) {
-		return; //do not compress, already compressed
-	}
-
-	if (img_format > Image::FORMAT_RGBA8) {
-		// TODO: we should be able to handle FORMAT_RGBA4444 and FORMAT_RGBA5551 eventually
-		return;
-	}
-
-	// FIXME: Commented out during Vulkan rebase.
-	/*
-	if (force_etc1_format) {
-		// If VRAM compression is using ETC, but image has alpha, convert to RGBA4444 or LA8
-		// This saves space while maintaining the alpha channel
-		if (detected_channels == Image::USED_CHANNELS_RGBA) {
-			if (p_img->has_mipmaps()) {
-				// Image doesn't support mipmaps with RGBA4444 textures
-				p_img->clear_mipmaps();
-			}
-			p_img->convert(Image::FORMAT_RGBA4444);
-			return;
-		} else if (detected_channels == Image::USE_CHANNELS_LA) {
-			p_img->convert(Image::FORMAT_LA8);
-			return;
-		}
-	}
-	*/
-
-	uint32_t imgw = p_img->get_width(), imgh = p_img->get_height();
-
-	Image::Format etc_format = force_etc1_format ? Image::FORMAT_ETC : _get_etc2_mode(p_channels);
-
-	Ref<Image> img = p_img->duplicate();
-
-	if (img->get_format() != Image::FORMAT_RGBA8) {
-		img->convert(Image::FORMAT_RGBA8); //still uses RGBA to convert
-	}
-
-	if (img->has_mipmaps()) {
-		if (next_power_of_2(imgw) != imgw || next_power_of_2(imgh) != imgh) {
-			img->resize_to_po2();
-			imgw = img->get_width();
-			imgh = img->get_height();
-		}
-	} else {
-		if (imgw % 4 != 0 || imgh % 4 != 0) {
-			if (imgw % 4) {
-				imgw += 4 - imgw % 4;
-			}
-			if (imgh % 4) {
-				imgh += 4 - imgh % 4;
-			}
-
-			img->resize(imgw, imgh);
-		}
-	}
-
-	const uint8_t *r = img->get_data().ptr();
-	ERR_FAIL_COND(!r);
-
-	unsigned int target_size = Image::get_image_data_size(imgw, imgh, etc_format, p_img->has_mipmaps());
-	int mmc = 1 + (p_img->has_mipmaps() ? Image::get_image_required_mipmaps(imgw, imgh, etc_format) : 0);
-
-	Vector<uint8_t> dst_data;
-	dst_data.resize(target_size);
-
-	uint8_t *w = dst_data.ptrw();
-
-	// prepare parameters to be passed to etc2comp
-	int num_cpus = OS::get_singleton()->get_processor_count();
-	int encoding_time = 0;
-	float effort = 0.0; //default, reasonable time
-
-	if (p_lossy_quality > 0.95) {
-		effort = 80;
-	} else if (p_lossy_quality > 0.85) {
-		effort = 60;
-	} else if (p_lossy_quality > 0.75) {
-		effort = 40;
-	}
-
-	Etc::ErrorMetric error_metric = Etc::ErrorMetric::RGBX; // NOTE: we can experiment with other error metrics
-	Etc::Image::Format etc2comp_etc_format = _image_format_to_etc2comp_format(etc_format);
-
-	int wofs = 0;
-
-	print_verbose("ETC: Begin encoding, format: " + Image::get_format_name(etc_format));
-	uint64_t t = OS::get_singleton()->get_ticks_msec();
-	for (int i = 0; i < mmc; i++) {
-		// convert source image to internal etc2comp format (which is equivalent to Image::FORMAT_RGBAF)
-		// NOTE: We can alternatively add a case to Image::convert to handle Image::FORMAT_RGBAF conversion.
-		int mipmap_ofs = 0, mipmap_size = 0, mipmap_w = 0, mipmap_h = 0;
-		img->get_mipmap_offset_size_and_dimensions(i, mipmap_ofs, mipmap_size, mipmap_w, mipmap_h);
-		const uint8_t *src = &r[mipmap_ofs];
-
-		Etc::ColorFloatRGBA *src_rgba_f = new Etc::ColorFloatRGBA[mipmap_w * mipmap_h];
-		for (int j = 0; j < mipmap_w * mipmap_h; j++) {
-			int si = j * 4; // RGBA8
-			src_rgba_f[j] = Etc::ColorFloatRGBA::ConvertFromRGBA8(src[si], src[si + 1], src[si + 2], src[si + 3]);
-		}
-
-		unsigned char *etc_data = nullptr;
-		unsigned int etc_data_len = 0;
-		unsigned int extended_width = 0, extended_height = 0;
-		Etc::Encode((float *)src_rgba_f, mipmap_w, mipmap_h, etc2comp_etc_format, error_metric, effort, num_cpus, num_cpus, &etc_data, &etc_data_len, &extended_width, &extended_height, &encoding_time);
-
-		CRASH_COND(wofs + etc_data_len > target_size);
-		memcpy(&w[wofs], etc_data, etc_data_len);
-		wofs += etc_data_len;
-
-		delete[] etc_data;
-		delete[] src_rgba_f;
-	}
-
-	print_verbose("ETC: Time encoding: " + rtos(OS::get_singleton()->get_ticks_msec() - t));
-
-	p_img->create(imgw, imgh, p_img->has_mipmaps(), etc_format, dst_data);
-}
-
-static void _compress_etc1(Image *p_img, float p_lossy_quality) {
-	_compress_etc(p_img, p_lossy_quality, true, Image::USED_CHANNELS_RGB);
-}
-
-static void _compress_etc2(Image *p_img, float p_lossy_quality, Image::UsedChannels p_channels) {
-	_compress_etc(p_img, p_lossy_quality, false, p_channels);
-}
-
-void _register_etc_compress_func() {
-	Image::_image_compress_etc1_func = _compress_etc1;
-	Image::_image_compress_etc2_func = _compress_etc2;
-}
diff --git a/modules/etc/texture_loader_pkm.cpp b/modules/etc/texture_loader_pkm.cpp
deleted file mode 100644
index 95db9315d5..0000000000
--- a/modules/etc/texture_loader_pkm.cpp
+++ /dev/null
@@ -1,114 +0,0 @@
-/*************************************************************************/
-/*  texture_loader_pkm.cpp                                               */
-/*************************************************************************/
-/*                       This file is part of:                           */
-/*                           GODOT ENGINE                                */
-/*                      https://godotengine.org                          */
-/*************************************************************************/
-/* Copyright (c) 2007-2021 Juan Linietsky, Ariel Manzur.                 */
-/* Copyright (c) 2014-2021 Godot Engine contributors (cf. AUTHORS.md).   */
-/*                                                                       */
-/* Permission is hereby granted, free of charge, to any person obtaining */
-/* a copy of this software and associated documentation files (the       */
-/* "Software"), to deal in the Software without restriction, including   */
-/* without limitation the rights to use, copy, modify, merge, publish,   */
-/* distribute, sublicense, and/or sell copies of the Software, and to    */
-/* permit persons to whom the Software is furnished to do so, subject to */
-/* the following conditions:                                             */
-/*                                                                       */
-/* The above copyright notice and this permission notice shall be        */
-/* included in all copies or substantial portions of the Software.       */
-/*                                                                       */
-/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
-/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
-/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
-/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
-/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
-/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
-/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
-/*************************************************************************/
-
-#include "texture_loader_pkm.h"
-
-#include "core/os/file_access.h"
-#include <string.h>
-
-struct ETC1Header {
-	char tag[6]; // "PKM 10"
-	uint16_t format = 0; // Format == number of mips (== zero)
-	uint16_t texWidth = 0; // Texture dimensions, multiple of 4 (big-endian)
-	uint16_t texHeight = 0;
-	uint16_t origWidth = 0; // Original dimensions (big-endian)
-	uint16_t origHeight = 0;
-};
-
-RES ResourceFormatPKM::load(const String &p_path, const String &p_original_path, Error *r_error, bool p_use_sub_threads, float *r_progress, CacheMode p_cache_mode) {
-	if (r_error) {
-		*r_error = ERR_CANT_OPEN;
-	}
-
-	Error err;
-	FileAccess *f = FileAccess::open(p_path, FileAccess::READ, &err);
-	if (!f) {
-		return RES();
-	}
-
-	FileAccessRef fref(f);
-	if (r_error) {
-		*r_error = ERR_FILE_CORRUPT;
-	}
-
-	ERR_FAIL_COND_V_MSG(err != OK, RES(), "Unable to open PKM texture file '" + p_path + "'.");
-
-	// big endian
-	f->set_endian_swap(true);
-
-	ETC1Header h;
-	f->get_buffer((uint8_t *)&h.tag, sizeof(h.tag));
-	ERR_FAIL_COND_V_MSG(strncmp(h.tag, "PKM 10", sizeof(h.tag)), RES(), "Invalid or unsupported PKM texture file '" + p_path + "'.");
-
-	h.format = f->get_16();
-	h.texWidth = f->get_16();
-	h.texHeight = f->get_16();
-	h.origWidth = f->get_16();
-	h.origHeight = f->get_16();
-
-	Vector<uint8_t> src_data;
-
-	uint32_t size = h.texWidth * h.texHeight / 2;
-	src_data.resize(size);
-	uint8_t *wb = src_data.ptrw();
-	f->get_buffer(wb, size);
-
-	int mipmaps = h.format;
-	int width = h.origWidth;
-	int height = h.origHeight;
-
-	Ref<Image> img = memnew(Image(width, height, mipmaps, Image::FORMAT_ETC, src_data));
-
-	Ref<ImageTexture> texture = memnew(ImageTexture);
-	texture->create_from_image(img);
-
-	if (r_error) {
-		*r_error = OK;
-	}
-
-	f->close();
-	memdelete(f);
-	return texture;
-}
-
-void ResourceFormatPKM::get_recognized_extensions(List<String> *p_extensions) const {
-	p_extensions->push_back("pkm");
-}
-
-bool ResourceFormatPKM::handles_type(const String &p_type) const {
-	return ClassDB::is_parent_class(p_type, "Texture2D");
-}
-
-String ResourceFormatPKM::get_resource_type(const String &p_path) const {
-	if (p_path.get_extension().to_lower() == "pkm") {
-		return "ImageTexture";
-	}
-	return "";
-}
diff --git a/modules/etc/texture_loader_pkm.h b/modules/etc/texture_loader_pkm.h
deleted file mode 100644
index 2ed5e75807..0000000000
--- a/modules/etc/texture_loader_pkm.h
+++ /dev/null
@@ -1,47 +0,0 @@
-/*************************************************************************/
-/*  texture_loader_pkm.h                                                 */
-/*************************************************************************/
-/*                       This file is part of:                           */
-/*                           GODOT ENGINE                                */
-/*                      https://godotengine.org                          */
-/*************************************************************************/
-/* Copyright (c) 2007-2021 Juan Linietsky, Ariel Manzur.                 */
-/* Copyright (c) 2014-2021 Godot Engine contributors (cf. AUTHORS.md).   */
-/*                                                                       */
-/* Permission is hereby granted, free of charge, to any person obtaining */
-/* a copy of this software and associated documentation files (the       */
-/* "Software"), to deal in the Software without restriction, including   */
-/* without limitation the rights to use, copy, modify, merge, publish,   */
-/* distribute, sublicense, and/or sell copies of the Software, and to    */
-/* permit persons to whom the Software is furnished to do so, subject to */
-/* the following conditions:                                             */
-/*                                                                       */
-/* The above copyright notice and this permission notice shall be        */
-/* included in all copies or substantial portions of the Software.       */
-/*                                                                       */
-/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
-/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
-/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
-/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
-/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
-/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
-/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
-/*************************************************************************/
-
-#ifndef TEXTURE_LOADER_PKM_H
-#define TEXTURE_LOADER_PKM_H
-
-#include "core/io/resource_loader.h"
-#include "scene/resources/texture.h"
-
-class ResourceFormatPKM : public ResourceFormatLoader {
-public:
-	virtual RES load(const String &p_path, const String &p_original_path = "", Error *r_error = nullptr, bool p_use_sub_threads = false, float *r_progress = nullptr, CacheMode p_cache_mode = CACHE_MODE_REUSE);
-	virtual void get_recognized_extensions(List<String> *p_extensions) const;
-	virtual bool handles_type(const String &p_type) const;
-	virtual String get_resource_type(const String &p_path) const;
-
-	virtual ~ResourceFormatPKM() {}
-};
-
-#endif // TEXTURE_LOADER_PKM_H
diff --git a/modules/etcpak/SCsub b/modules/etcpak/SCsub
new file mode 100644
index 0000000000..821c6801b4
--- /dev/null
+++ b/modules/etcpak/SCsub
@@ -0,0 +1,52 @@
+#!/usr/bin/env python
+
+Import("env")
+Import("env_modules")
+
+env_etcpak = env_modules.Clone()
+
+# Thirdparty source files
+
+thirdparty_obj = []
+
+thirdparty_dir = "#thirdparty/etcpak/"
+thirdparty_sources = [
+    "Bitmap.cpp",
+    "BitmapDownsampled.cpp",
+    "BlockData.cpp",
+    "ColorSpace.cpp",
+    "DataProvider.cpp",
+    "Debug.cpp",
+    "Dither.cpp",
+    "Error.cpp",
+    "mmap.cpp",
+    "ProcessDxtc.cpp",
+    "ProcessRGB.cpp",
+    "System.cpp",
+    "Tables.cpp",
+    "TaskDispatch.cpp",
+    "Timing.cpp",
+    "lz4/lz4.c",
+]
+thirdparty_sources = [thirdparty_dir + file for file in thirdparty_sources]
+
+env_etcpak.Prepend(CPPPATH=[thirdparty_dir])
+
+# Also requires libpng headers
+if env["builtin_libpng"]:
+    env_etcpak.Prepend(CPPPATH=["#thirdparty/libpng"])
+
+env_thirdparty = env_etcpak.Clone()
+env_thirdparty.disable_warnings()
+env_thirdparty.add_source_files(thirdparty_obj, thirdparty_sources)
+env.modules_sources += thirdparty_obj
+
+# Godot source files
+
+module_obj = []
+
+env_etcpak.add_source_files(module_obj, "*.cpp")
+env.modules_sources += module_obj
+
+# Needed to force rebuilding the module files when the thirdparty library is updated.
+env.Depends(module_obj, thirdparty_obj)
diff --git a/modules/etc/config.py b/modules/etcpak/config.py
index 53b8f2f2e3..53b8f2f2e3 100644
--- a/modules/etc/config.py
+++ b/modules/etcpak/config.py
diff --git a/modules/etcpak/image_etcpak.cpp b/modules/etcpak/image_etcpak.cpp
new file mode 100644
index 0000000000..251d2cd7b0
--- /dev/null
+++ b/modules/etcpak/image_etcpak.cpp
@@ -0,0 +1,170 @@
+/*************************************************************************/
+/*  image_etcpak.cpp                                                     */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2021 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2021 Godot Engine contributors (cf. AUTHORS.md).   */
+/*                                                                       */
+/* Permission is hereby granted, free of charge, to any person obtaining */
+/* a copy of this software and associated documentation files (the       */
+/* "Software"), to deal in the Software without restriction, including   */
+/* without limitation the rights to use, copy, modify, merge, publish,   */
+/* distribute, sublicense, and/or sell copies of the Software, and to    */
+/* permit persons to whom the Software is furnished to do so, subject to */
+/* the following conditions:                                             */
+/*                                                                       */
+/* The above copyright notice and this permission notice shall be        */
+/* included in all copies or substantial portions of the Software.       */
+/*                                                                       */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
+/*************************************************************************/
+
+#include "image_etcpak.h"
+
+#include "core/os/copymem.h"
+#include "core/os/os.h"
+#include "core/string/print_string.h"
+
+#include "thirdparty/etcpak/ProcessDxtc.hpp"
+#include "thirdparty/etcpak/ProcessRGB.hpp"
+
+// thresholds for the early compression-mode decision scheme in QuickETC2
+// which can be changed by the option -e
+float ecmd_threshold[3] = { 0.03f, 0.09f, 0.38f };
+
+EtcpakType _determine_etc_type(Image::UsedChannels p_source) {
+	switch (p_source) {
+		case Image::USED_CHANNELS_L:
+			return EtcpakType::ETCPAK_TYPE_ETC1;
+		case Image::USED_CHANNELS_LA:
+			return EtcpakType::ETCPAK_TYPE_ETC2_ALPHA;
+		case Image::USED_CHANNELS_R:
+			return EtcpakType::ETCPAK_TYPE_ETC2;
+		case Image::USED_CHANNELS_RG:
+			return EtcpakType::ETCPAK_TYPE_ETC2_RA_AS_RG;
+		case Image::USED_CHANNELS_RGB:
+			return EtcpakType::ETCPAK_TYPE_ETC2;
+		case Image::USED_CHANNELS_RGBA:
+			return EtcpakType::ETCPAK_TYPE_ETC2_ALPHA;
+		default:
+			return EtcpakType::ETCPAK_TYPE_ETC2_ALPHA;
+	}
+}
+
+EtcpakType _determine_dxt_type(Image::UsedChannels p_source) {
+	switch (p_source) {
+		case Image::USED_CHANNELS_L:
+			return EtcpakType::ETCPAK_TYPE_DXT1;
+		case Image::USED_CHANNELS_LA:
+			return EtcpakType::ETCPAK_TYPE_DXT5;
+		case Image::USED_CHANNELS_R:
+			return EtcpakType::ETCPAK_TYPE_DXT5;
+		case Image::USED_CHANNELS_RG:
+			return EtcpakType::ETCPAK_TYPE_DXT5_RA_AS_RG;
+		case Image::USED_CHANNELS_RGB:
+			return EtcpakType::ETCPAK_TYPE_DXT5;
+		case Image::USED_CHANNELS_RGBA:
+			return EtcpakType::ETCPAK_TYPE_DXT5;
+		default:
+			return EtcpakType::ETCPAK_TYPE_DXT5;
+	}
+}
+void _compress_etc2(Image *p_img, float p_lossy_quality, Image::UsedChannels p_source) {
+	EtcpakType type = _determine_etc_type(p_source);
+	_compress_etcpak(type, p_img, p_lossy_quality, false, p_source);
+}
+void _compress_bc(Image *p_img, float p_lossy_quality, Image::UsedChannels p_source) {
+	EtcpakType type = _determine_dxt_type(p_source);
+	_compress_etcpak(type, p_img, p_lossy_quality, false, p_source);
+}
+void _compress_etc1(Image *p_img, float p_lossy_quality) {
+	_compress_etcpak(EtcpakType::ETCPAK_TYPE_ETC1, p_img, p_lossy_quality, true, Image::USED_CHANNELS_RGB);
+}
+
+void _compress_etcpak(EtcpakType p_compresstype, Image *p_img, float p_lossy_quality, bool force_etc1_format, Image::UsedChannels p_channels) {
+	uint64_t t = OS::get_singleton()->get_ticks_msec();
+	Image::Format img_format = p_img->get_format();
+
+	if (img_format >= Image::FORMAT_DXT1) {
+		return; //do not compress, already compressed
+	}
+
+	if (img_format > Image::FORMAT_RGBA8) {
+		// TODO: we should be able to handle FORMAT_RGBA4444 and FORMAT_RGBA5551 eventually
+		return;
+	}
+
+	Image::Format format = Image::FORMAT_RGBA8;
+	if (p_img->get_format() != Image::FORMAT_RGBA8) {
+		p_img->convert(Image::FORMAT_RGBA8);
+	}
+	if (p_compresstype == EtcpakType::ETCPAK_TYPE_ETC1 || force_etc1_format) {
+		format = Image::FORMAT_ETC;
+	} else if (p_compresstype == EtcpakType::ETCPAK_TYPE_ETC2) {
+		format = Image::FORMAT_ETC2_RGB8;
+	} else if (p_compresstype == EtcpakType::ETCPAK_TYPE_ETC2_RA_AS_RG) {
+		format = Image::FORMAT_ETC2_RA_AS_RG;
+		p_img->convert_rg_to_ra_rgba8();
+	} else if (p_compresstype == EtcpakType::ETCPAK_TYPE_ETC2_ALPHA) {
+		format = Image::FORMAT_ETC2_RGBA8;
+	} else if (p_compresstype == EtcpakType::ETCPAK_TYPE_DXT1) {
+		format = Image::FORMAT_DXT1;
+	} else if (p_compresstype == EtcpakType::ETCPAK_TYPE_DXT5_RA_AS_RG) {
+		format = Image::FORMAT_DXT5_RA_AS_RG;
+		p_img->convert_rg_to_ra_rgba8();
+	} else if (p_compresstype == EtcpakType::ETCPAK_TYPE_DXT5) {
+		format = Image::FORMAT_DXT5;
+	} else {
+		ERR_FAIL();
+	}
+
+	const bool mipmap = p_img->has_mipmaps();
+	print_verbose("Encoding format: " + Image::get_format_name(format));
+
+	Ref<Image> new_img;
+	new_img.instance();
+	new_img->create(p_img->get_width(), p_img->get_height(), mipmap, format);
+	Vector<uint8_t> data = new_img->get_data();
+	uint8_t *wr = data.ptrw();
+
+	Ref<Image> image = p_img->duplicate();
+	int mmc = 1 + (mipmap ? Image::get_image_required_mipmaps(new_img->get_width(), new_img->get_height(), format) : 0);
+	for (int i = 0; i < mmc; i++) {
+		int ofs, size, mip_w, mip_h;
+		new_img->get_mipmap_offset_size_and_dimensions(i, ofs, size, mip_w, mip_h);
+		mip_w = (mip_w + 3) & ~3;
+		mip_h = (mip_h + 3) & ~3;
+		Vector<uint8_t> dst_data;
+		dst_data.resize(size);
+		int mipmap_ofs = image->get_mipmap_offset(i);
+
+		const uint32_t *image_read = (const uint32_t *)&image->get_data().ptr()[mipmap_ofs];
+		uint64_t *dst_write = (uint64_t *)dst_data.ptrw();
+		if (p_compresstype == EtcpakType::ETCPAK_TYPE_ETC1 || force_etc1_format) {
+			CompressEtc1RgbDither(image_read, dst_write, mip_w * mip_h / 16, mip_w);
+		} else if (p_compresstype == EtcpakType::ETCPAK_TYPE_ETC2 || p_compresstype == EtcpakType::ETCPAK_TYPE_ETC2_RA_AS_RG) {
+			CompressEtc2Rgb(image_read, dst_write, mip_w * mip_h / 16, mip_w);
+		} else if (p_compresstype == EtcpakType::ETCPAK_TYPE_ETC2_ALPHA) {
+			CompressEtc2Rgba(image_read, dst_write, mip_w * mip_h / 16, mip_w);
+		} else if (p_compresstype == EtcpakType::ETCPAK_TYPE_DXT5 || p_compresstype == EtcpakType::ETCPAK_TYPE_DXT5_RA_AS_RG) {
+			CompressDxt5(image_read, dst_write, mip_w * mip_h / 16, mip_w);
+		} else if (p_compresstype == EtcpakType::ETCPAK_TYPE_DXT1) {
+			CompressDxt1Dither(image_read, dst_write, mip_w * mip_h / 16, mip_w);
+		} else {
+			ERR_FAIL();
+		}
+		copymem(&wr[ofs], dst_data.ptr(), size);
+	}
+	p_img->create(new_img->get_width(), new_img->get_height(), mipmap, format, data);
+
+	print_verbose(vformat("ETCPAK encode took %s ms.", rtos(OS::get_singleton()->get_ticks_msec() - t)));
+}
diff --git a/modules/etc/register_types.cpp b/modules/etcpak/image_etcpak.h
index b165bccb3e..0137bab7cc 100644
--- a/modules/etc/register_types.cpp
+++ b/modules/etcpak/image_etcpak.h
@@ -1,5 +1,5 @@
 /*************************************************************************/
-/*  register_types.cpp                                                   */
+/*  image_etcpak.h                                                       */
 /*************************************************************************/
 /*                       This file is part of:                           */
 /*                           GODOT ENGINE                                */
@@ -28,21 +28,24 @@
 /* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
 /*************************************************************************/
 
-#include "register_types.h"
+#ifndef IMAGE_ETCPAK_H
+#define IMAGE_ETCPAK_H
 
-#include "image_compress_etc.h"
-#include "texture_loader_pkm.h"
+#include "core/io/image.h"
 
-static Ref<ResourceFormatPKM> resource_loader_pkm;
+enum class EtcpakType {
+	ETCPAK_TYPE_ETC1,
+	ETCPAK_TYPE_ETC2,
+	ETCPAK_TYPE_ETC2_ALPHA,
+	ETCPAK_TYPE_ETC2_RA_AS_RG,
+	ETCPAK_TYPE_DXT1,
+	ETCPAK_TYPE_DXT5,
+	ETCPAK_TYPE_DXT5_RA_AS_RG,
+};
 
-void register_etc_types() {
-	resource_loader_pkm.instance();
-	ResourceLoader::add_resource_format_loader(resource_loader_pkm);
+void _compress_etcpak(EtcpakType p_compresstype, Image *p_img, float p_lossy_quality, bool force_etc1_format, Image::UsedChannels p_channels);
+void _compress_etc1(Image *p_img, float p_lossy_quality);
+void _compress_etc2(Image *p_img, float p_lossy_quality, Image::UsedChannels p_source);
+void _compress_bc(Image *p_img, float p_lossy_quality, Image::UsedChannels p_source);
 
-	_register_etc_compress_func();
-}
-
-void unregister_etc_types() {
-	ResourceLoader::remove_resource_format_loader(resource_loader_pkm);
-	resource_loader_pkm.unref();
-}
+#endif // IMAGE_ETCPAK_H
diff --git a/modules/etc/image_compress_etc.h b/modules/etcpak/register_types.cpp
index 44a06194e9..fcc0bc8b6f 100644
--- a/modules/etc/image_compress_etc.h
+++ b/modules/etcpak/register_types.cpp
@@ -1,5 +1,5 @@
 /*************************************************************************/
-/*  image_compress_etc.h                                                 */
+/*  register_types.cpp                                                   */
 /*************************************************************************/
 /*                       This file is part of:                           */
 /*                           GODOT ENGINE                                */
@@ -28,9 +28,15 @@
 /* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
 /*************************************************************************/
 
-#ifndef IMAGE_COMPRESS_ETC_H
-#define IMAGE_COMPRESS_ETC_H
+#include "register_types.h"
 
-void _register_etc_compress_func();
+#include "image_etcpak.h"
 
-#endif // IMAGE_COMPRESS_ETC_H
+void register_etcpak_types() {
+	Image::_image_compress_etc1_func = _compress_etc1;
+	Image::_image_compress_etc2_func = _compress_etc2;
+	Image::_image_compress_bc_func = _compress_bc;
+}
+
+void unregister_etcpak_types() {
+}
diff --git a/modules/etc/register_types.h b/modules/etcpak/register_types.h
index e8cbb635ae..9b300a3275 100644
--- a/modules/etc/register_types.h
+++ b/modules/etcpak/register_types.h
@@ -28,10 +28,5 @@
 /* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
 /*************************************************************************/
 
-#ifndef ETC_REGISTER_TYPES_H
-#define ETC_REGISTER_TYPES_H
-
-void register_etc_types();
-void unregister_etc_types();
-
-#endif // ETC_REGISTER_TYPES_H
+void register_etcpak_types();
+void unregister_etcpak_types();
diff --git a/modules/squish/image_compress_squish.cpp b/modules/squish/image_compress_squish.cpp
index cce08034df..fb0c7aba1d 100644
--- a/modules/squish/image_compress_squish.cpp
+++ b/modules/squish/image_compress_squish.cpp
@@ -76,83 +76,3 @@ void image_decompress_squish(Image *p_image) {
 		p_image->convert_ra_rgba8_to_rg();
 	}
 }
-
-void image_compress_squish(Image *p_image, float p_lossy_quality, Image::UsedChannels p_channels) {
-	if (p_image->get_format() >= Image::FORMAT_DXT1) {
-		return; //do not compress, already compressed
-	}
-
-	int w = p_image->get_width();
-	int h = p_image->get_height();
-
-	if (p_image->get_format() <= Image::FORMAT_RGBA8) {
-		int squish_comp = squish::kColourRangeFit;
-
-		if (p_lossy_quality > 0.85) {
-			squish_comp = squish::kColourIterativeClusterFit;
-		} else if (p_lossy_quality > 0.75) {
-			squish_comp = squish::kColourClusterFit;
-		}
-
-		Image::Format target_format = Image::FORMAT_RGBA8;
-
-		p_image->convert(Image::FORMAT_RGBA8); //still uses RGBA to convert
-
-		switch (p_channels) {
-			case Image::USED_CHANNELS_L: {
-				target_format = Image::FORMAT_DXT1;
-				squish_comp |= squish::kDxt1;
-			} break;
-			case Image::USED_CHANNELS_LA: {
-				target_format = Image::FORMAT_DXT5;
-				squish_comp |= squish::kDxt5;
-			} break;
-			case Image::USED_CHANNELS_R: {
-				target_format = Image::FORMAT_RGTC_R;
-				squish_comp |= squish::kBc4;
-			} break;
-			case Image::USED_CHANNELS_RG: {
-				target_format = Image::FORMAT_RGTC_RG;
-				squish_comp |= squish::kBc5;
-			} break;
-			case Image::USED_CHANNELS_RGB: {
-				target_format = Image::FORMAT_DXT1;
-				squish_comp |= squish::kDxt1;
-			} break;
-			case Image::USED_CHANNELS_RGBA: {
-				//TODO, should convert both, then measure which one does a better job
-				target_format = Image::FORMAT_DXT5;
-				squish_comp |= squish::kDxt5;
-
-			} break;
-			default: {
-				ERR_PRINT("Unknown image format, defaulting to RGBA8");
-				break;
-			}
-		}
-
-		Vector<uint8_t> data;
-		int target_size = Image::get_image_data_size(w, h, target_format, p_image->has_mipmaps());
-		int mm_count = p_image->has_mipmaps() ? Image::get_image_required_mipmaps(w, h, target_format) : 0;
-		data.resize(target_size);
-		int shift = Image::get_format_pixel_rshift(target_format);
-
-		const uint8_t *rb = p_image->get_data().ptr();
-		uint8_t *wb = data.ptrw();
-
-		int dst_ofs = 0;
-
-		for (int i = 0; i <= mm_count; i++) {
-			int bw = w % 4 != 0 ? w + (4 - w % 4) : w;
-			int bh = h % 4 != 0 ? h + (4 - h % 4) : h;
-
-			int src_ofs = p_image->get_mipmap_offset(i);
-			squish::CompressImage(&rb[src_ofs], w, h, &wb[dst_ofs], squish_comp);
-			dst_ofs += (MAX(4, bw) * MAX(4, bh)) >> shift;
-			w = MAX(w / 2, 1);
-			h = MAX(h / 2, 1);
-		}
-
-		p_image->create(p_image->get_width(), p_image->get_height(), p_image->has_mipmaps(), target_format, data);
-	}
-}
diff --git a/modules/squish/image_compress_squish.h b/modules/squish/image_compress_squish.h
index 301d30fcf1..ebc5a41887 100644
--- a/modules/squish/image_compress_squish.h
+++ b/modules/squish/image_compress_squish.h
@@ -33,7 +33,6 @@
 
 #include "core/io/image.h"
 
-void image_compress_squish(Image *p_image, float p_lossy_quality, Image::UsedChannels p_channels);
 void image_decompress_squish(Image *p_image);
 
 #endif // IMAGE_COMPRESS_SQUISH_H
diff --git a/modules/squish/register_types.cpp b/modules/squish/register_types.cpp
index 451e9d8e93..c51cdc9521 100644
--- a/modules/squish/register_types.cpp
+++ b/modules/squish/register_types.cpp
@@ -32,7 +32,6 @@
 #include "image_compress_squish.h"
 
 void register_squish_types() {
-	Image::set_compress_bc_func(image_compress_squish);
 	Image::_image_decompress_bc = image_decompress_squish;
 }