LibSoftGPU: Add Image class

This serves as the storage for all image types. 1D, 2D, 3D, Cube and
image arrays.

Upon construction a full mipmap chain is generated and the image is
immutable afterwards with respect to its layout.

Userland/Libraries/LibSoftGPU/ImageFormat.h

@@ -0,0 +1,122 @@
+/*
+ * Copyright (c) 2021, Stephan Unverwerth <s.unverwerth@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibGfx/Vector4.h>
+
+namespace SoftGPU {
+
+enum class ImageFormat {
+    RGB565,
+    RGB888,
+    BGR888,
+    RGBA8888,
+    BGRA8888,
+};
+
+inline static constexpr size_t element_size(ImageFormat format)
+{
+    switch (format) {
+    case ImageFormat::RGB565:
+        return 2;
+    case ImageFormat::RGB888:
+    case ImageFormat::BGR888:
+        return 3;
+    case ImageFormat::RGBA8888:
+    case ImageFormat::BGRA8888:
+        return 4;
+    default:
+        VERIFY_NOT_REACHED();
+    }
+}
+
+inline static FloatVector4 unpack_color(void const* ptr, ImageFormat format)
+{
+    switch (format) {
+    case ImageFormat::RGB888: {
+        auto rgb = reinterpret_cast<u8 const*>(ptr);
+        return {
+            rgb[0] / 255.f,
+            rgb[1] / 255.f,
+            rgb[2] / 255.f,
+            1.0f
+        };
+    }
+    case ImageFormat::BGR888: {
+        auto bgr = reinterpret_cast<u8 const*>(ptr);
+        return {
+            bgr[2] / 255.f,
+            bgr[1] / 255.f,
+            bgr[0] / 255.f,
+            1.0f
+        };
+    }
+    case ImageFormat::RGBA8888: {
+        auto rgba = *reinterpret_cast<u32 const*>(ptr);
+        return {
+            (rgba & 0xff) / 255.f,
+            ((rgba >> 8) & 0xff) / 255.f,
+            ((rgba >> 16) & 0xff) / 255.f,
+            ((rgba >> 24) & 0xff) / 255.f
+        };
+    }
+    case ImageFormat::BGRA8888: {
+        auto bgra = *reinterpret_cast<u32 const*>(ptr);
+        return {
+            ((bgra >> 16) & 0xff) / 255.f,
+            ((bgra >> 8) & 0xff) / 255.f,
+            (bgra & 0xff) / 255.f,
+            ((bgra >> 24) & 0xff) / 255.f
+        };
+    }
+    case ImageFormat::RGB565: {
+        auto rgb = *reinterpret_cast<u16 const*>(ptr);
+        return {
+            ((rgb >> 11) & 0x1f) / 31.f,
+            ((rgb >> 5) & 0x3f) / 63.f,
+            (rgb & 0x1f) / 31.f,
+            1.0f
+        };
+    }
+    default:
+        VERIFY_NOT_REACHED();
+    }
+}
+
+inline static void pack_color(FloatVector4 const& color, void* ptr, ImageFormat format)
+{
+    auto r = static_cast<u8>(clamp(color.x(), 0.0f, 1.0f) * 255);
+    auto g = static_cast<u8>(clamp(color.y(), 0.0f, 1.0f) * 255);
+    auto b = static_cast<u8>(clamp(color.z(), 0.0f, 1.0f) * 255);
+    auto a = static_cast<u8>(clamp(color.w(), 0.0f, 1.0f) * 255);
+
+    switch (format) {
+    case ImageFormat::RGB888:
+        reinterpret_cast<u8*>(ptr)[0] = r;
+        reinterpret_cast<u8*>(ptr)[1] = g;
+        reinterpret_cast<u8*>(ptr)[2] = b;
+        return;
+    case ImageFormat::BGR888:
+        reinterpret_cast<u8*>(ptr)[2] = b;
+        reinterpret_cast<u8*>(ptr)[1] = g;
+        reinterpret_cast<u8*>(ptr)[0] = r;
+        return;
+    case ImageFormat::RGBA8888:
+        *reinterpret_cast<u32*>(ptr) = r | (g << 8) | (b << 16) | (a << 24);
+        return;
+    case ImageFormat::BGRA8888:
+        *reinterpret_cast<u32*>(ptr) = b | (g << 8) | (r << 16) | (a << 24);
+        return;
+    case ImageFormat::RGB565:
+        *reinterpret_cast<u16*>(ptr) = (r & 0x1f) | ((g & 0x3f) << 5) | ((b & 0x1f) << 11);
+        return;
+    default:
+        VERIFY_NOT_REACHED();
+    }
+}
+
+}