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/Image.cpp

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2021, Stephan Unverwerth <s.unverwerth@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibSoftGPU/Image.h>
+
+namespace SoftGPU {
+
+Image::Image(ImageFormat format, unsigned width, unsigned height, unsigned depth, unsigned levels, unsigned layers)
+    : m_format(format)
+    , m_width(width)
+    , m_height(height)
+    , m_depth(depth)
+    , m_num_layers(layers)
+{
+    VERIFY(width > 0);
+    VERIFY(height > 0);
+    VERIFY(depth > 0);
+    VERIFY(levels > 0);
+    VERIFY(layers > 0);
+
+    m_mipmap_sizes.append({ width, height, depth });
+    m_mipmap_offsets.append(0);
+
+    m_mipchain_size += width * height * depth * element_size(format);
+
+    while (--levels && (width > 1 || height > 1 || depth > 1)) {
+        width = max(width / 2, 1);
+        height = max(height / 2, 1);
+        depth = max(depth / 2, 1);
+        m_mipmap_sizes.append({ width, height, depth });
+        m_mipmap_offsets.append(m_mipchain_size);
+
+        m_mipchain_size += width * height * depth * element_size(format);
+    }
+
+    m_num_levels = m_mipmap_sizes.size();
+
+    m_data.resize(m_mipchain_size * m_num_layers);
+}
+
+}