转换

图像格式和类型转换操作。

函数映射

libvips C	Dart 绑定	Pipeline 方法	PipelineSpec
`vips_crop()`	`apiBindings.crop()`	`pipeline.crop()`	`spec.crop()`
`vips_extract_area()`	`apiBindings.extractArea()`	-	-
`vips_smartcrop()`	`apiBindings.smartcrop()`	`pipeline.smartCrop()`	`spec.smartCrop()`
`vips_flip()`	`apiBindings.flip()`	`pipeline.flip()`	`spec.flip()`
`vips_embed()`	`apiBindings.embed()`	`pipeline.embed()`	`spec.embed()`
`vips_gravity()`	`apiBindings.gravity()`	`pipeline.gravity()`	`spec.gravity()`
`vips_zoom()`	`apiBindings.zoom()`	`pipeline.zoom()`	`spec.zoom()`
`vips_autorot()`	`apiBindings.autorot()`	`pipeline.autoRotate()`	`spec.autoRotate()`
`vips_cast()`	`conversionBindings.cast()`	`pipeline.cast()`	`spec.cast()`
`vips_bandjoin()`	`conversionBindings.bandjoin()`	-	-

从图像中提取矩形区域。

// (left, top, width, height)
pipeline.crop(100, 100, 400, 300)

自动裁剪到最有趣的区域。

// (width, height)
pipeline.smartCrop(400, 300)

Interesting 选项：

水平或垂直翻转图像。

pipeline.flipHorizontal()
pipeline.flipVertical()

根据 EXIF 方向标签自动旋转。

pipeline.autoRotate()

将图像嵌入更大的画布。

apiBindings.embed(input, output, x, y, width, height);

使用重力方向将图像放置在更大的画布中。

apiBindings.gravity(input, output, direction, width, height);

方向： VipsCompassDirection.centre, north, south, east, west 等。