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JPG: Perform lossless orientation changes where possible (#29)
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25 changes: 0 additions & 25 deletions
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src/commonMain/kotlin/com/ashampoo/kim/common/BinaryFileParser.kt
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163 changes: 163 additions & 0 deletions
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src/commonMain/kotlin/com/ashampoo/kim/format/jpeg/JpegOrientationOffsetFinder.kt
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,163 @@ | ||
| /* | ||
| * Copyright 2023 Ashampoo GmbH & Co. KG | ||
| * | ||
| * 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 com.ashampoo.kim.format.jpeg | ||
|
|
||
| import com.ashampoo.kim.common.ByteOrder | ||
| import com.ashampoo.kim.common.ImageReadException | ||
| import com.ashampoo.kim.common.toSingleNumberHexes | ||
| import com.ashampoo.kim.common.tryWithImageReadException | ||
| import com.ashampoo.kim.format.ImageFormatMagicNumbers | ||
| import com.ashampoo.kim.format.jpeg.JpegConstants.JPEG_BYTE_ORDER | ||
| import com.ashampoo.kim.format.tiff.TiffReader | ||
| import com.ashampoo.kim.format.tiff.constants.TiffConstants.TIFF_ENTRY_LENGTH | ||
| import com.ashampoo.kim.format.tiff.constants.TiffConstants.TIFF_HEADER_SIZE | ||
| import com.ashampoo.kim.format.tiff.constants.TiffTag | ||
| import com.ashampoo.kim.input.ByteReader | ||
|
|
||
| /** | ||
| * This algorithm quickly identifies the EXIF orientation offset. | ||
| * If the file already has one no restructuring of the whole file is necessary. | ||
| */ | ||
| object JpegOrientationOffsetFinder { | ||
|
|
||
| const val SEGMENT_IDENTIFIER = 0xFF.toByte() | ||
| const val SEGMENT_START_OF_SCAN = 0xDA.toByte() | ||
| const val MARKER_END_OF_IMAGE = 0xD9.toByte() | ||
| const val APP1_MARKER = 0xE1.toByte() | ||
|
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||
| @OptIn(ExperimentalStdlibApi::class) | ||
| @Throws(ImageReadException::class) | ||
| @Suppress("ComplexMethod") | ||
| fun findOrientationOffset( | ||
| byteReader: ByteReader | ||
| ): Long? = tryWithImageReadException { | ||
|
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| val magicNumberBytes = byteReader.readBytes(ImageFormatMagicNumbers.jpegShort.size).toList() | ||
|
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| /* Ensure it's actually a JPEG. */ | ||
| require(magicNumberBytes == ImageFormatMagicNumbers.jpegShort) { | ||
| "JPEG magic number mismatch: ${magicNumberBytes.toByteArray().toSingleNumberHexes()}" | ||
| } | ||
|
|
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| var orientationOffset: Long? = null | ||
|
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| var positionCounter: Long = ImageFormatMagicNumbers.jpegShort.size.toLong() | ||
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| @Suppress("LoopWithTooManyJumpStatements") | ||
| do { | ||
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| var segmentIdentifier = byteReader.readByte() ?: break | ||
| var segmentType = byteReader.readByte() ?: break | ||
|
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| positionCounter += 2 | ||
|
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| /* | ||
| * Find the segment marker. Markers are zero or more 0xFF bytes, followed by | ||
| * a 0xFF and then a byte not equal to 0x00 or 0xFF. | ||
| */ | ||
| while ( | ||
| segmentIdentifier != SEGMENT_IDENTIFIER || | ||
| segmentType == SEGMENT_IDENTIFIER || | ||
| segmentType.toInt() == 0 | ||
| ) { | ||
|
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| segmentIdentifier = segmentType | ||
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| val nextSegmentType = byteReader.readByte() ?: break | ||
|
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| positionCounter++ | ||
|
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| segmentType = nextSegmentType | ||
| } | ||
|
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| if (segmentType == SEGMENT_START_OF_SCAN || segmentType == MARKER_END_OF_IMAGE) | ||
| break | ||
|
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| /* Note: Segment length includes size bytes */ | ||
| val segmentLength = | ||
| byteReader.read2BytesAsInt("segmentLength", JPEG_BYTE_ORDER) - 2 | ||
|
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| positionCounter += 2 | ||
|
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| if (segmentLength <= 0) | ||
| throw ImageReadException("Illegal JPEG segment length: $segmentLength") | ||
|
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| /* We are only looking for the EXIF segment. */ | ||
| if (segmentType != APP1_MARKER) { | ||
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| byteReader.skipBytes("skip segment", segmentLength.toLong()) | ||
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| positionCounter += segmentLength | ||
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| continue | ||
| } | ||
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| val exifIdentifierBytes = byteReader.readBytes("EXIF identifier", 6) | ||
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| positionCounter += 6 | ||
|
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| /* Skip the APP1 XMP segment. */ | ||
| if (!exifIdentifierBytes.contentEquals(JpegConstants.EXIF_IDENTIFIER_CODE)) { | ||
| byteReader.skipBytes("skip segment", segmentLength.toLong() - 6) | ||
| positionCounter += segmentLength - 6 | ||
| continue | ||
| } | ||
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| val tiffHeader = TiffReader.readTiffHeader(byteReader) | ||
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| val exifByteOrder = tiffHeader.byteOrder | ||
|
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| byteReader.skipBytes( | ||
| "skip bytes to first IFD", | ||
| tiffHeader.offsetToFirstIFD - TIFF_HEADER_SIZE | ||
| ) | ||
|
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| val entryCount = byteReader.read2BytesAsInt("entrycount", exifByteOrder) | ||
|
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| positionCounter += tiffHeader.offsetToFirstIFD + 2 | ||
|
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| for (entryIndex in 0 until entryCount) { | ||
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| val tag = byteReader.read2BytesAsInt("Entry $entryIndex: 'tag'", exifByteOrder) | ||
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| if (tag == TiffTag.TIFF_TAG_ORIENTATION.tag) { | ||
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| orientationOffset = positionCounter + 8 | ||
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| if (exifByteOrder == ByteOrder.BIG_ENDIAN) | ||
| orientationOffset++ | ||
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| return orientationOffset | ||
|
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| } else { | ||
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| byteReader.skipBytes("skip TIFF entry", TIFF_ENTRY_LENGTH - 2L) | ||
|
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| positionCounter += TIFF_ENTRY_LENGTH | ||
| } | ||
| } | ||
|
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| /* | ||
| * We are now past the EXIF segment. | ||
| * If we reach this point there is no orientation flag. | ||
| */ | ||
| return null | ||
|
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||
| } while (true) | ||
|
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| return null | ||
| } | ||
| } |
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