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Get JPEG image dimensions in Dart
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| // translated to Dart from a code snippet presented here: | |
| // https://stackoverflow.com/questions/672916/how-to-get-image-height-and-width-using-java | |
| Future<Size> getJpegDimensions(File jpegFile) async { | |
| final f = await jpegFile.open(); | |
| Size dimension; | |
| try { | |
| // check for SOI marker | |
| if (await f.readByte() != 255 || await f.readByte() != 216) { | |
| throw new FormatException( | |
| "SOI (Start Of Image) marker 0xff 0xd8 missing"); | |
| } | |
| while (await f.readByte() == 255) { | |
| int marker = await f.readByte(); | |
| int len = await f.readByte() << 8 | await f.readByte(); | |
| if (marker == 192) { | |
| // skip one byte | |
| await f.setPosition(await f.position() + 1); | |
| final height = await f.readByte() << 8 | await f.readByte(); | |
| final width = await f.readByte() << 8 | await f.readByte(); | |
| dimension = Size(width.toDouble(), height.toDouble()); | |
| break; | |
| } | |
| // skip len - 2 bytes | |
| await f.setPosition(await f.position() + len - 2); | |
| } | |
| } finally { | |
| await f.close(); | |
| } | |
| return dimension; | |
| } |
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