1 /* 2 * Copyright (C) 2009 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package android.opengl; 18 19 import java.nio.Buffer; 20 21 /** 22 * Methods for encoding and decoding ETC1 textures. 23 * <p> 24 * The standard for the ETC1 texture format can be found at 25 * http://www.khronos.org/registry/gles/extensions/OES/OES_compressed_ETC1_RGB8_texture.txt 26 * <p> 27 * The PKM file format is of a 16-byte header that describes the image bounds 28 * followed by the encoded ETC1 texture data. 29 * <p> 30 * @see ETC1Util 31 */ 32 public class ETC1 { 33 34 /** 35 * Size in bytes of an encoded block. 36 */ 37 public static final int ENCODED_BLOCK_SIZE = 8; 38 39 /** 40 * Size in bytes of a decoded block. 41 */ 42 public static final int DECODED_BLOCK_SIZE = 48; 43 44 /** 45 * Size of a PKM file header, in bytes. 46 */ 47 public static final int ETC_PKM_HEADER_SIZE = 16; 48 49 /** 50 * Accepted by the internalformat parameter of glCompressedTexImage2D. 51 */ 52 public static final int ETC1_RGB8_OES = 0x8D64; 53 54 /** 55 * Encode a block of pixels. 56 * 57 * @param in a native order direct buffer of size DECODED_BLOCK_SIZE that represent a 58 * 4 x 4 square of 3-byte pixels in form R, G, B. Byte (3 * (x + 4 * y) is the R 59 * value of pixel (x, y). 60 * 61 * @param validPixelMask is a 16-bit mask where bit (1 << (x + y * 4)) indicates whether 62 * the corresponding (x,y) pixel is valid. Invalid pixel color values are ignored when compressing. 63 * 64 * @param out a native order direct buffer of size ENCODED_BLOCK_SIZE that receives the 65 * ETC1 compressed version of the data. 66 * 67 */ encodeBlock(Buffer in, int validPixelMask, Buffer out)68 public static native void encodeBlock(Buffer in, int validPixelMask, Buffer out); 69 70 /** 71 * Decode a block of pixels. 72 * 73 * @param in a native order direct buffer of size ENCODED_BLOCK_SIZE that contains the 74 * ETC1 compressed version of the data. 75 * 76 * @param out a native order direct buffer of size DECODED_BLOCK_SIZE that will receive 77 * the decoded data. The data represents a 78 * 4 x 4 square of 3-byte pixels in form R, G, B. Byte (3 * (x + 4 * y) is the R 79 * value of pixel (x, y). 80 */ decodeBlock(Buffer in, Buffer out)81 public static native void decodeBlock(Buffer in, Buffer out); 82 83 /** 84 * Return the size of the encoded image data (does not include size of PKM header). 85 */ getEncodedDataSize(int width, int height)86 public static native int getEncodedDataSize(int width, int height); 87 88 /** 89 * Encode an entire image. 90 * @param in a native order direct buffer of the image data. Formatted such that 91 * pixel (x,y) is at pIn + pixelSize * x + stride * y; 92 * @param out a native order direct buffer of the encoded data. 93 * Must be large enough to store entire encoded image. 94 * @param pixelSize must be 2 or 3. 2 is an GL_UNSIGNED_SHORT_5_6_5 image, 95 * 3 is a GL_BYTE RGB image. 96 */ encodeImage(Buffer in, int width, int height, int pixelSize, int stride, Buffer out)97 public static native void encodeImage(Buffer in, int width, int height, 98 int pixelSize, int stride, Buffer out); 99 100 /** 101 * Decode an entire image. 102 * @param in native order direct buffer of the encoded data. 103 * @param out native order direct buffer of the image data. Will be written such that 104 * pixel (x,y) is at pIn + pixelSize * x + stride * y. Must be 105 * large enough to store entire image. 106 * @param pixelSize must be 2 or 3. 2 is an GL_UNSIGNED_SHORT_5_6_5 image, 107 * 3 is a GL_BYTE RGB image. 108 */ decodeImage(Buffer in, Buffer out, int width, int height, int pixelSize, int stride)109 public static native void decodeImage(Buffer in, Buffer out, 110 int width, int height, int pixelSize, int stride); 111 112 /** 113 * Format a PKM header 114 * @param header native order direct buffer of the header. 115 * @param width the width of the image in pixels. 116 * @param height the height of the image in pixels. 117 */ formatHeader(Buffer header, int width, int height)118 public static native void formatHeader(Buffer header, int width, int height); 119 120 /** 121 * Check if a PKM header is correctly formatted. 122 * @param header native order direct buffer of the header. 123 */ isValid(Buffer header)124 public static native boolean isValid(Buffer header); 125 126 /** 127 * Read the image width from a PKM header 128 * @param header native order direct buffer of the header. 129 */ getWidth(Buffer header)130 public static native int getWidth(Buffer header); 131 132 /** 133 * Read the image height from a PKM header 134 * @param header native order direct buffer of the header. 135 */ getHeight(Buffer header)136 public static native int getHeight(Buffer header); 137 } 138