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/*
* Copyright (C) 2009 The Android Open Source Project
*
* 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);
}
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