A library for encoding and decoding ETC1 textures.

The ETC1 compressed texture format is commonly
supported by OpenGL ES 2.0-capable devices.

1 files changed, 137 insertions, 0 deletions

diff --git a/opengl/java/android/opengl/ETC1.java b/opengl/java/android/opengl/ETC1.java
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+++ b/opengl/java/android/opengl/ETC1.java
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+/*
+ *  Copyright 2009 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.opengl;
+
+import java.nio.Buffer;
+
+/**
+ * Methods for encoding and decoding ETC1 textures.
+ * <p>
+ * The standard for the ETC1 texture format can be found at
+ * http://www.khronos.org/registry/gles/extensions/OES/OES_compressed_ETC1_RGB8_texture.txt
+ * <p>
+ * The PKM file format is of a 16-byte header that describes the image bounds
+ * followed by the encoded ETC1 texture data.
+ * <p>
+ * @see(ETC1Util)
+ */
+public class ETC1 {
+
+    /**
+     * Size in bytes of an encoded block.
+     */
+    public static final int ENCODED_BLOCK_SIZE = 8;
+
+    /**
+     * Size in bytes of a decoded block.
+     */
+    public static final int DECODED_BLOCK_SIZE = 48;
+
+    /**
+     * Size of a PKM file header, in bytes.
+     */
+    public static final int ETC_PKM_HEADER_SIZE = 16;
+
+    /**
+     * Accepted by the internalformat parameter of glCompressedTexImage2D.
+     */
+    public static final int ETC1_RGB8_OES = 0x8D64;
+
+    /**
+     * Encode a block of pixels.
+     *
+     * @param in a native order direct buffer of size DECODED_BLOCK_SIZE that represent a
+     * 4 x 4 square of 3-byte pixels in form R, G, B. Byte (3 * (x + 4 * y) is the R
+     * value of pixel (x, y).
+     *
+     * @param validPixelMask is a 16-bit mask where bit (1 << (x + y * 4)) indicates whether
+     * the corresponding (x,y) pixel is valid. Invalid pixel color values are ignored when compressing.
+     *
+     * @param out a native order direct buffer of size ENCODED_BLOCK_SIZE that receives the
+     * ETC1 compressed version of the data.
+     *
+     */
+    public static native void encodeBlock(Buffer in, int validPixelMask, Buffer out);
+
+    /**
+     * Decode a block of pixels.
+     *
+     * @param in a native order direct buffer of size ENCODED_BLOCK_SIZE that contains the
+     * ETC1 compressed version of the data.
+     *
+     * @param out a native order direct buffer of size DECODED_BLOCK_SIZE that will receive
+     * the decoded data. The data represents a
+     * 4 x 4 square of 3-byte pixels in form R, G, B. Byte (3 * (x + 4 * y) is the R
+     * value of pixel (x, y).
+     */
+    public static native void decodeBlock(Buffer in, Buffer out);
+
+    /**
+     * Return the size of the encoded image data (does not include size of PKM header).
+     */
+    public static native int getEncodedDataSize(int width, int height);
+
+    /**
+     * Encode an entire image.
+     * @param in a native order direct buffer of the image data. Formatted such that
+     *           pixel (x,y) is at pIn + pixelSize * x + stride * y;
+     * @param out a native order direct buffer of the encoded data.
+     * Must be large enough to store entire encoded image.
+     * @param pixelSize must be 2 or 3. 2 is an GL_UNSIGNED_SHORT_5_6_5 image,
+     * 3 is a GL_BYTE RGB image.
+     */
+    public static native void encodeImage(Buffer in, int width, int height,
+            int pixelSize, int stride, Buffer out);
+
+    /**
+     * Decode an entire image.
+     * @param in native order direct buffer of the encoded data.
+     * @param out native order direct buffer of the image data. Will be written such that
+     * pixel (x,y) is at pIn + pixelSize * x + stride * y. Must be
+     * large enough to store entire image.
+     * @param pixelSize must be 2 or 3. 2 is an GL_UNSIGNED_SHORT_5_6_5 image,
+     * 3 is a GL_BYTE RGB image.
+     */
+    public static native void decodeImage(Buffer in, Buffer out,
+            int width, int height, int pixelSize, int stride);
+
+    /**
+     * Format a PKM header
+     * @param header native order direct buffer of the header.
+     * @param width the width of the image in pixels.
+     * @param height the height of the image in pixels.
+     */
+    public static native void formatHeader(Buffer header, int width, int height);
+
+    /**
+     * Check if a PKM header is correctly formatted.
+     * @param header native order direct buffer of the header.
+     */
+    public static native boolean isValid(Buffer header);
+
+    /**
+     * Read the image width from a PKM header
+     * @param header native order direct buffer of the header.
+     */
+    public static native int getWidth(Buffer header);
+
+    /**
+     * Read the image height from a PKM header
+     * @param header native order direct buffer of the header.
+     */
+    public static native int getHeight(Buffer header);
+}