Table of Contents

Class JpegTransformOptions

Namespace
Egami.Formats.Jpeg
Assembly
Egami.dll

Options for JpegTransform: the rotation or flip, a crop, dropping color, how partial edge blocks are handled, how the result is coded and whether metadata is copied. The defaults copy the image unchanged, with optimized Huffman tables.

public sealed class JpegTransformOptions
Inheritance
JpegTransformOptions
Inherited Members

Examples

// Turns the photo upright by its EXIF orientation without re-encoding: no quality is lost, and the tag is reset.
JpegTransform.Apply("sideways.jpg", "upright.jpg", new JpegTransformOptions { Operation = JpegTransformOperation.AutoOrient });

// Rotates, crops and drops the color in one pass; a file can be transformed in place.
JpegTransformResult result = JpegTransform.Apply("upright.jpg", "upright.jpg", new JpegTransformOptions
{
    Operation = JpegTransformOperation.Rotate90,
    Crop = new Rect(0, 0, 200, 120),
    Grayscale = true,
});
Console.WriteLine($"{result.Width} × {result.Height}");

Properties

Arithmetic

Gets whether the result is arithmetic-coded (jpegtran -arithmetic; SOF9, or SOF10 with Progressive), as Arithmetic writes: about 4 to 8% smaller than optimized Huffman tables, with the same pixels, so a Huffman file can be repacked with no loss; but no web browser reads it. OptimizeHuffman is then ignored. Defaults to false: Huffman-coded, whatever the source was, as jpegtran does.

public bool Arithmetic { get; init; }

Property Value

bool

CopyMetadata

Gets whether EXIF, ICC, XMP, IPTC, comments and other application segments are copied (jpegtran -copy all). Defaults to true. EXIF's pixel dimensions follow the result; its thumbnail gets the same rotation, flip and gray conversion, and is dropped after a crop, since it would still show the whole image. With false only the JFIF or Adobe segment that says how to read the colors is written.

public bool CopyMetadata { get; init; }

Property Value

bool

Crop

Gets the area to keep, in the coordinates of the image after Operation, or null (the default) for all of it. Its left and top edges move left and up to the MCU grid, as with jpegtran -crop, so the result can be up to 15 pixels wider and taller than asked; its right and bottom edges are kept as given.

public Rect? Crop { get; init; }

Property Value

Rect?

Default

Gets the default options: no change, edges trimmed, optimized Huffman tables, metadata copied.

public static JpegTransformOptions Default { get; }

Property Value

JpegTransformOptions

Edges

Gets what happens to partial MCUs at a mirrored edge. Defaults to Trim.

public JpegTransformEdges Edges { get; init; }

Property Value

JpegTransformEdges

Grayscale

Gets whether the result keeps only the luma component, a gray image with no loss, as jpegtran -grayscale does. Applies to YCbCr files; gray files are unchanged, and RGB, CMYK and YCCK files throw NotSupportedException.

public bool Grayscale { get; init; }

Property Value

bool

Operation

Gets the rotation or flip. Defaults to None.

public JpegTransformOperation Operation { get; init; }

Property Value

JpegTransformOperation

OptimizeHuffman

Gets whether a sequential result gets Huffman tables made for it (jpegtran -optimize), which makes it a few percent smaller than the standard tables do. Defaults to true, so a transformed file is not larger than its source for the tables alone. 12-bit files always get their own; progressive ones always do too.

public bool OptimizeHuffman { get; init; }

Property Value

bool

Progressive

Gets whether the result is written progressive, with the scan script and per-scan tables of Progressive. Defaults to false: sequential, whatever the source was, as jpegtran does without -progressive.

public bool Progressive { get; init; }

Property Value

bool
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