Resize, crop, rotation

Responsive design necessitates displaying pictures in many sizes, usually much smaller than the original. Rather than delivering large, full-sized images and relying on the browser to resize them, you can programmatically scale them immediately without needing to use editing tools.

Going further, you can automate art direction with advanced scaling features such as smart resize, smart crop, and object zoom.

Typical use cases:

• Use -/preview/ when you need to put an image inside a known tile without changing its proportions, and ok with empty space. E.g. you have a layout of 300x400, and neither horizontal nor vertical photos shouldn’t escape these borders.
• When you need image to fill the whole tile, use -/scale_crop/.
• Do you want to keep proportions but fill the whole tile? Try -/smart_resize/ that will generate missing parts of the picture.
• Need to bring attention to the key elements of the picture, like a face? Use -/scale_crop/smart/ to crop a background, but keep important objects.
• Need perfect user pics? Combine -/crop/face/, -/border_radius/, and -/setfill/ operations.

These operations, like other URL API functions, are non-destructive, handled on the server side, and sent to the browser in the requested size.

Note: The order of operations is essential. For instance, when you resize an image first, the ensuing crop operation will use the coordinates of the resized image.

Preview

-/preview/
-/preview/:dimensions/

Downscales an image proportionally to fit the given width and height in pixels. Use it as a default resizing method when you need to save image proportions without calculating precise width or height.

• :dimensions — width and height in pixels separated by x.
  Example: 320x240.
  If the dimensions are not specified, it’ll be 2048x2048.

  /:uuid/-/preview/ /:uuid/-/preview/300x500/

Resize

-/resize/:one_or_two_dimensions/

Resizes an image to one or two dimensions. When you set both width and height explicitly, it may result in a distorted image. If you specify either side, this operation will preserve the original aspect ratio and resize the image accordingly.

• :one_or_two_dimensions — width and height in pixels separated by x, one of the values can be omitted.
  Examples: 320x240, 320x, x240.

  /:uuid/-/resize/320x240/ /:uuid/-/resize/320x/ /:uuid/-/resize/x240/

Change resize behavior

-/stretch/:mode/

Sets the resize and scale_crop behavior when a source image is smaller than the requested dimensions. The order is important: a stretch operation applies to its following resize or scale_crop. You can use multiple resizing operations with individual stretch behavior for each one.

• :mode — one of the following values:
  • on — an image can be scaled up (default).
  • off — an image won’t be scaled up.
  • fill — no image scaling up. The background color fills the remaining parts.

Smart resize

-/smart_resize/:dimensions/

Content-aware resize helps retaining original proportions of faces and other visually sensible objects while resizing the rest of the image using intelligent algorithms.

• :dimensions — width and height in pixels separated by x.
  Example: 320x240.

Smart resize works best for solid, gradient, and homogenous backgrounds that’ll be expanded. If background stretching can’t be done without artifacts, a solid fill with a matching color will be applied instead.

Note that we are working on improving Smart resize and behavior may change. Contact us if you found out regression.

Crop

-/crop/:dimensions/
-/crop/:dimensions/:alignment/

Crops an image by using specified dimensions and alignment.

• :dimensions — width and height in pixels or percents separated by x.
  Percent values are based on original size and should end with % or p char.
  Examples: 320x240, 50px240, 30%x25%.
• :alignment — horizontal and vertical offsets in pixels or percents separated by ,.
  Offset in pixels is allowed to be negative. Percent values are a position of cropped area in full image canvas and should end with % or p char.
  Examples: 100,-50, 50p,240, 30%,25%.
  A single semantic shortcut is also allowed as an alignment value: center, top, right, bottom, left.
  If alignment is not specified, 0,0 value is used.

In URLs, % is an escape character and should be encoded with %25 escape sequence, e.g. -/crop/200x200/80%25,80%25/. For convenience, you can use the p shortcut for percent which doesn’t require encoding.

If given dimensions are greater than the ones of the original image, the image is rendered inside a color-filled box. The color of that box can be changed via the setfill operation.

Crop by ratio

-/crop/:ratio/
-/crop/:ratio/:alignment/

Crops the image to the specified aspect ratio, cutting off the rest of the image.

• :ratio — two numbers greater than zero separated by :.
  Ratio is the quotient from the division of these numbers.
• :alignment — horizontal and vertical offsets in pixels or percents separated by ,.
  Offset in pixels is allowed to be negative. Percent values are a position of cropped area in full image canvas and should end with % or p char.
  Examples: 100,-50, 50p,240, 30%,25%.
  A single semantic shortcut is also allowed as an alignment value: center, top, right, bottom, left.
  If alignment is not specified, center value is used.

In URLs, % is an escape character and should be encoded with %25 escape sequence, e.g. -/crop/4:3/80%25,80%25/. For convenience, you can use the p shortcut for percent which doesn’t require encoding.

Crop by objects

-/crop/:tag/
-/crop/:tag/:ratio/
-/crop/:tag/:ratio/:alignment/
-/crop/:tag/:dimensions/
-/crop/:tag/:dimensions/:alignment/

Crops the image to the object specified by the :tag parameter.

• :tag — one of the following values:
  • face — the largest detected face in the image is used as a crop basis.
  • image — the whole image is used as a crop basis.
• :ratio — two numbers greater than zero separated by :. Ratio is the quotient from the division of these numbers. The found object fits into the given aspect ratio.
• :dimensions — width and height in percents separated by x.
  Percent values are based on the tag size and should end with % or p char.
  Examples: 150%x150%, 200%x100%.
• :alignment — horizontal and vertical offsets in percentage values separated by comma (,).
  The offsets represent a position of cropped area that is based on the selected tag location (for instance, a face). The offset percentage values should end with % or p char.
  Examples: 30%,25%, 30p,25p
  A single semantic shortcut is also allowed as an alignment value: center, top, right, bottom, left.
  If alignment is not specified, center value is used.

In URLs, % is an escape character and should be encoded with %25 escape sequence, e.g. -/crop/face/4:3/80%25,80%25/. For convenience, you can use the p shortcut for percent which doesn’t require encoding.

Scale crop

-/scale_crop/:dimensions/
-/scale_crop/:dimensions/:alignment/

Scales an image until it fully covers the specified dimensions; the rest gets cropped. Mostly used to place images with various dimensions into placeholders (e.g., square shaped).

• :dimensions — width and height in pixels separated by x.
  Examples: 320x240, 440x440.
• :alignment — horizontal and vertical offsets in percentage values separated by comma (,).
  The offsets represent a position of cropped area that is based on the selected tag location (for instance, a face). The offset percentage values should end with % or p char.
  Examples: 30%,25%, 30p,25p
  A single semantic shortcut is also allowed as an alignment value: center, top, right, bottom, left.
  If alignment is not specified, 0,0 value is used.

In URLs, % is an escape character and should be encoded with %25 escape sequence, e.g. -/scale_crop/440x440/80%25,80%25/. For convenience, you can use the p shortcut for percent which doesn’t require encoding.

Smart crop

-/scale_crop/:dimensions/:type/
-/scale_crop/:dimensions/:type/:alignment/

Switching the crop type to one of the smart modes enables the content-aware mechanics. Uploadcare applies AI-based algorithms to detect faces and other visually sensible objects to crop the background and not the main object.

• :dimensions — width and height in pixels separated by x.
  Examples: 320x240, 440x440.
• :type — one of the following values:
  • smart (alias for smart_faces_objects_points)
  • smart_faces_objects
  • smart_faces_points
  • smart_objects_faces_points
  • smart_objects_faces
  • smart_objects_points
  • smart_points
  • smart_objects
  • smart_faces
• :alignment — horizontal and vertical offsets in percentage values separated by comma (,).
  The offsets represent a position of cropped area that is based on the selected tag location (for instance, a face). The offset percentage values should end with % or p char.
  Examples: 30%,25%, 30p,25p
  A single semantic shortcut is also allowed as an alignment value: center, top, right, bottom, left.
  If alignment is not specified, 0,0 value is used. Alignment doesn’t affect smart crop behavior and works as a fallback when no smart crop can’t detect any objects.

In URLs, % is an escape character and should be encoded with %25 escape sequence, e.g. -/scale_crop/440x440/smart/80%25,80%25/. For convenience, you can use the p shortcut for percent which doesn’t require encoding.

Content-aware mechanics of the smart crop are based on the following methods of image analysis:

• Face Detection, :type is set to smart_faces. Face detection identifies and locates human faces in digital images.
• Object Detection, :type is set to smart_object. Object detection identifies and locates most visually important regions in the image.
• Corner Points Detection, :type is set to smart_points. This method analyses image pixels to find the high contrast corners in the image, useful for abstract, landscape, and art images. The corner points have much less semantic information than other methods and designed to be used as a fallback.

The methods you include separating by underscore are applied sequentially. The algorithm switches to the next method only if no regions were found by the previous one. For example smart_faces_objects_points applies face detection initially as the first step. Only when no faces are found on an image, the object detection will be used. Finally, when no objects are found, the corner points will be detected.

Smart crop always tries to save the maximum amount of pixels from the original image. It first applies scale operation and then cuts horizontal or vertical excesses.

Crop solid background

-/trim/
-/trim/:tolerance/:padding/

Removes insignificant edges of the image, such as solid backgrounds or fully transparent areas.

By default, this operation only removes colors very close to the background. It can be adjusted with a color distribution :tolerance parameter, ranging from 0 to 99.

Since objects cropped to the edges can look unnatural, you can optionally add :padding, specified as a percentage of the resulting image, ranging from 0% to 100%.

Border radius and circle crop

-/border_radius/:radii/
-/border_radius/:radii/:vertical_radii/

Applies transparency mask with round or elliptical corners to the image.

The syntax and effect is pretty much similar to the border-radius property in CSS. E.g. border-radius: 10px 100px / 50%; would become -/border_radius/10,100/50%/. The differences are:

• One should use a comma instead of a space to separate arguments. No spaces allowed.
• Only percents and absolute values are allowed.
• px for absolute values should be omitted.

If :vertical_radii is omitted, :radii used for both horizontal and vertical radii. Both :radii and :vertical_radii should contatin 1 to 4 numbers separated by comma. Each number could be an absolute radius in pixels or a percentage value ended with % or p char.

• The first number in each argument represents all 4 corner radii, or NW and SE corner radii, or just NW radius depending on next values presence.
• The second number represents NE and SW corner radii, or just NE radius depending on next values presence.
• The third number represents SE corner radius.
• The fourth number represents SW corner radius.

In URLs, % is an escape character and should be encoded with %25 escape sequence, e.g. -/border_radius/10%25/50%25/. For convenience, you can use the p shortcut for percent which doesn’t require encoding.

Set fill color when croping and stretching

-/setfill/:color/

Sets the fill color used with crop, stretch or when converting an alpha channel enabled image to JPEG.

• :color — color in hexadecimal notation with optional transparency.
  Example: 99ff99, 9f9, 99ff9920.

Zoom objects

-/zoom_objects/:zoom/

Zoom objects operation is best suited for images with solid or uniform backgrounds.

• :zoom — sets the object’s size in the image from 1 to 100.

As a result of the operation, the object’s size in the image will change. The resolution of the image after the operation will remain the same. For example, an object in an image with applied operation -/zoom_objects/100/ is the object that occupies the maximum area of this image.

Automatic rotation, EXIF-based

-/autorotate/yes/
-/autorotate/no/

The default behavior goes with parsing EXIF tags of original images and rotating them according to the “Orientation” tag. This is what we call autorotation. -/autorotate/no/ allows turning off the default behavior.

Manual rotation

-/rotate/:angle/

Right-angle image rotation, counterclockwise. The value of :angle must be a multiple of 90.

Flip

-/flip/

Flips images.

Mirror

-/mirror/

Mirrors images.