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图像操作

rotate¶

Rotate the output image by either an explicit angle or auto-orient based on the EXIF Orientation tag.

If an angle is provided, it is converted to a valid 90/180/270deg rotation. For example, -450 will produce a 270deg rotation.

If no angle is provided, it is determined from the EXIF data. Mirroring is supported and may infer the use of a flip operation.

The use of rotate implies the removal of the EXIF Orientation tag, if any.

Method order is important when both rotating and extracting regions, for example rotate(x).extract(y) will produce a different result to extract(y).rotate(x).

参数

angle Number angle of rotation, must be a multiple of 90. (optional, default auto)

示例

const pipeline = sharp()
  .rotate()
  .resize(null, 200)
  .toBuffer(function (err, outputBuffer, info) {
    // outputBuffer contains 200px high JPEG image data,
    // auto-rotated using EXIF Orientation tag
    // info.width and info.height contain the dimensions of the resized image
  });
readableStream.pipe(pipeline);

Throws Error Invalid parameters

返回 Sharp

extract¶

Extract a region of the image.

Use extract before resize for pre-resize extraction.
Use extract after resize for post-resize extraction.
Use extract before and after for both.

参数

options Object
- options.left Number zero-indexed offset from left edge
- options.top Number zero-indexed offset from top edge
- options.width Number dimension of extracted image
- options.height Number dimension of extracted image

示例

sharp(input)
  .extract({ left: left, top: top, width: width, height: height })
  .toFile(output, function(err) {
    // Extract a region of the input image, saving in the same format.
  });

sharp(input)
  .extract({ left: leftOffsetPre, top: topOffsetPre, width: widthPre, height: heightPre })
  .resize(width, height)
  .extract({ left: leftOffsetPost, top: topOffsetPost, width: widthPost, height: heightPost })
  .toFile(output, function(err) {
    // Extract a region, resize, then extract from the resized image
  });

Throws Error Invalid parameters

返回 Sharp

flip¶

Flip the image about the vertical Y axis. This always occurs after rotation, if any. The use of flip implies the removal of the EXIF Orientation tag, if any.

参数

flip Boolean (optional, default true)

返回 Sharp

flop¶

Flop the image about the horizontal X axis. This always occurs after rotation, if any. The use of flop implies the removal of the EXIF Orientation tag, if any.

参数

flop Boolean (optional, default true)

返回 Sharp

sharpen¶

Sharpen the image. When used without parameters, performs a fast, mild sharpen of the output image. When a sigma is provided, performs a slower, more accurate sharpen of the L channel in the LAB colour space. Separate control over the level of sharpening in "flat" and "jagged" areas is available.

参数

sigma Number? the sigma of the Gaussian mask, where sigma = 1 + radius / 2.
flat Number the level of sharpening to apply to "flat" areas. (optional, default 1.0)
jagged Number the level of sharpening to apply to "jagged" areas. (optional, default 2.0)
Throws Error Invalid parameters

返回 Sharp

blur¶

Blur the image. When used without parameters, performs a fast, mild blur of the output image. When a sigma is provided, performs a slower, more accurate Gaussian blur.

参数

sigma Number? a value between 0.3 and 1000 representing the sigma of the Gaussian mask, where sigma = 1 + radius / 2.
Throws Error Invalid parameters

返回 Sharp

extend¶

Extends/pads the edges of the image with the colour provided to the background method. This operation will always occur after resizing and extraction, if any.

参数

extend (Number | Object) single pixel count to add to all edges or an Object with per-edge counts
- extend.top Number?
- extend.left Number?
- extend.bottom Number?
- extend.right Number?

示例

// Resize to 140 pixels wide, then add 10 transparent pixels
// to the top, left and right edges and 20 to the bottom edge
sharp(input)
  .resize(140)
  .background({r: 0, g: 0, b: 0, alpha: 0})
  .extend({top: 10, bottom: 20, left: 10, right: 10})
  ...

Throws Error Invalid parameters

返回 Sharp

flatten¶

Merge alpha transparency channel, if any, with background.

参数

flatten Boolean (optional, default true)

返回 Sharp

trim¶

Trim "boring" pixels from all edges that contain values within a percentage similarity of the top-left pixel.

参数

tolerance Number value between 1 and 99 representing the percentage similarity. (optional, default 10)
Throws Error Invalid parameters

返回 Sharp

gamma¶

Apply a gamma correction by reducing the encoding (darken) pre-resize at a factor of 1/gamma then increasing the encoding (brighten) post-resize at a factor of gamma. This can improve the perceived brightness of a resized image in non-linear colour spaces. JPEG and WebP input images will not take advantage of the shrink-on-load performance optimisation when applying a gamma correction.

参数

gamma Number value between 1.0 and 3.0. (optional, default 2.2)
Throws Error Invalid parameters

返回 Sharp

negate¶

Produce the "negative" of the image.

参数

negate Boolean (optional, default true)

返回 Sharp

normalise¶

Enhance output image contrast by stretching its luminance to cover the full dynamic range.

参数

normalise Boolean (optional, default true)

返回 Sharp

normalize¶

Alternative spelling of normalise.

参数

normalize Boolean (optional, default true)

返回 Sharp

convolve¶

Convolve the image with the specified kernel.

参数

kernel Object
- kernel.width Number width of the kernel in pixels.
- kernel.height Number width of the kernel in pixels.
- kernel.kernel Array<Number> Array of length width*height containing the kernel values.
- kernel.scale Number the scale of the kernel in pixels. (optional, default sum)
- kernel.offset Number the offset of the kernel in pixels. (optional, default 0)

示例

sharp(input)
  .convolve({
    width: 3,
    height: 3,
    kernel: [-1, 0, 1, -2, 0, 2, -1, 0, 1]
  })
  .raw()
  .toBuffer(function(err, data, info) {
    // data contains the raw pixel data representing the convolution
    // of the input image with the horizontal Sobel operator
  });

Throws Error Invalid parameters

返回 Sharp

threshold¶

Any pixel value greather than or equal to the threshold value will be set to 255, otherwise it will be set to 0.

参数

threshold Number a value in the range 0-255 representing the level at which the threshold will be applied. (optional, default 128)
options Object?
- options.greyscale Boolean convert to single channel greyscale. (optional, default true)
- options.grayscale Boolean alternative spelling for greyscale. (optional, default true)
Throws Error Invalid parameters

返回 Sharp

boolean¶

Perform a bitwise boolean operation with operand image.

This operation creates an output image where each pixel is the result of the selected bitwise boolean operation between the corresponding pixels of the input images.

参数

operand (Buffer | String) Buffer containing image data or String containing the path to an image file.
operator String one of and, or or eor to perform that bitwise operation, like the C logic operators &, | and ^ respectively.
options Object?
- options.raw Object? describes operand when using raw pixel data.
  - options.raw.width Number?
  - options.raw.height Number?
  - options.raw.channels Number?
Throws Error Invalid parameters

返回 Sharp