gimpitemtransform: GIMP Library Reference Manual

## gimpitemtransform gimpitemtransform — Functions to perform transformations on items. |

## Functions

gint32 | gimp_item_transform_translate ()
gint32 | gimp_item_transform_flip_simple ()
gint32 | gimp_item_transform_flip ()
gint32 | gimp_item_transform_perspective ()
gint32 | gimp_item_transform_rotate_simple ()
gint32 | gimp_item_transform_rotate ()
gint32 | gimp_item_transform_scale ()
gint32 | gimp_item_transform_shear ()
gint32 | gimp_item_transform_2d ()
gint32 | gimp_item_transform_matrix ()

## Description

Functions to perform transformations on items.

## Functions

### gimp_item_transform_translate ()

    gint32
    gimp_item_transform_translate (gint32 item_ID,
                                   gdouble off_x,
                                   gdouble off_y);

Translate the item by the specified offsets.

This procedure translates the item by the amounts specified in the off_x and off_y arguments. These can be negative, and are considered offsets from the current position. The offsets will be rounded to the nearest pixel unless the item is a path.

If the item is attached to an image and has its linked flag set to TRUE, all additional items contained in the image which have the linked flag set to TRUE will also be translated by the specified offsets.

#### Parameters

item_ID | The item. |
off_x | Offset in x direction. |
off_y | Offset in y direction. |

#### Returns

The translated item.

Since: 2.10

### gimp_item_transform_flip_simple ()

    gint32
    gimp_item_transform_flip_simple (gint32 item_ID,
                                     GimpOrientationType flip_type,
                                     gboolean auto_center,
                                     gdouble axis);

Flip the specified item either vertically or horizontally.

This procedure flips the specified item.

If a selection exists and the item is a drawable, the portion of the drawable which lies under the selection is cut from the drawable and made into a floating selection which is then flipped. If auto_center is set to TRUE, the flip is around the selection's center. Otherwise, the coordinate of the axis needs to be specified. The return value is the ID of the flipped floating selection.

If there is no selection or the item is not a drawable, the entire item will be flipped around its center if auto_center is set to TRUE, otherwise the coordinate of the axis needs to be specified. Additionally, if the item has its linked flag set to TRUE, all additional items contained in the image which have the linked flag set to TRUE will also be flipped around the same axis. The return value will be equal to the item ID supplied as input.

This procedure is affected by the following context setters: `gimp_context_set_transform_resize()`.

#### Parameters

item_ID | The affected item. |
flip_type | Type of flip. |
auto_center | Whether to automatically position the axis in the selection center. |
axis | coord. of flip axis. |

#### Returns

The flipped item.

Since: 2.2

### gimp_item_transform_flip ()

    gint32
    gimp_item_transform_flip (gint32 item_ID,
                              gdouble x0,
                              gdouble y0,
                              gdouble x1,
                              gdouble y1);

Flip the specified item around a given line.

This procedure flips the specified item.

If a selection exists and the item is a drawable, the portion of the drawable which lies under the selection is cut from the drawable and made into a floating selection which is then flipped. The axis to flip around is specified by specifying two points from that line. The return value is the ID of the flipped floating selection.

If there is no selection or the item is not a drawable, the entire item will be flipped around the specified axis. Additionally, if the item has its linked flag set to TRUE, all additional items contained in the image which have the linked flag set to TRUE will also be flipped around the same axis. The return value will be equal to the item ID supplied as input.

This procedure is affected by the following context setters: `gimp_context_set_interpolation()`, `gimp_context_set_transform_direction()`, `gimp_context_set_transform_resize()`.

#### Parameters

item_ID | The affected item. |
x0 | horz. coord. of one end of axis. |
y0 | vert. coord. of one end of axis. |
x1 | horz. coord. of other end of axis. |
y1 | vert. coord. of other end of axis. |

#### Returns

The flipped item.

Since: 2.8

### gimp_item_transform_perspective ()

    gint32
    gimp_item_transform_perspective (gint32 item_ID,
                                     gdouble x0,
                                     gdouble y0,
                                     gdouble x1,
                                     gdouble y1,
                                     gdouble x2,
                                     gdouble y2,
                                     gdouble x3,
                                     gdouble y3);

Perform a possibly non-affine transformation on the specified item.

This procedure performs a possibly non-affine transformation on the specified item by allowing the corners of the original bounding box to be arbitrarily remapped to any values.

The 4 coordinates specify the new locations of each corner of the original bounding box. By specifying these values, any affine transformation (rotation, scaling, translation) can be affected. Additionally, these values can be specified such that the resulting transformed item will appear to have been projected via a perspective transform.

If a selection exists and the item is a drawable, the portion of the drawable which lies under the selection is cut from the drawable and made into a floating selection which is then transformed as specified. The return value is the ID of the transformed floating selection.

If there is no selection or the item is not a drawable, the entire item will be transformed according to the specified mapping. Additionally, if the item has its linked flag set to TRUE, all additional items contained in the image which have the linked flag set to TRUE will also be transformed the same way. The return value will be equal to the item ID supplied as input.

This procedure is affected by the following context setters: `gimp_context_set_interpolation()`, `gimp_context_set_transform_direction()`, `gimp_context_set_transform_resize()`.

#### Parameters

item_ID | The affected item. |
x0 | The new x coordinate of upper-left corner of original bounding box. |
y0 | The new y coordinate of upper-left corner of original bounding box. |
x1 | The new x coordinate of upper-right corner of original bounding box. |
y1 | The new y coordinate of upper-right corner of original bounding box. |
x2 | The new x coordinate of lower-left corner of original bounding box. |
y2 | The new y coordinate of lower-left corner of original bounding box. |
x3 | The new x coordinate of lower-right corner of original bounding box. |
y3 | The new y coordinate of lower-right corner of original bounding box. |

#### Returns

The transformed item.

Since: 2.8

### gimp_item_transform_rotate_simple ()

    gint32
    gimp_item_transform_rotate_simple (gint32 item_ID,
                                       GimpRotationType rotate_type,
                                       gboolean auto_center,
                                       gdouble center_x,
                                       gdouble center_y);

Rotate the specified item about given coordinates through the specified angle.

This function rotates the specified item.

If a selection exists and the item is a drawable, the portion of the drawable which lies under the selection is cut from the drawable and made into a floating selection which is then rotated by the specified amount. If auto_center is set to TRUE, the rotation is around the selection's center. Otherwise, the coordinate of the center point needs to be specified. The return value is the ID of the rotated floating selection.

If there is no selection or the item is not a drawable, the entire item will be rotated around its center if auto_center is set to TRUE, otherwise the coordinate of the center point needs to be specified. Additionally, if the item has its linked flag set to TRUE, all additional items contained in the image which have the linked flag set to TRUE will also be rotated around the same center point. The return value will be equal to the item ID supplied as input.

This procedure is affected by the following context setters: `gimp_context_set_transform_resize()`.

#### Parameters

item_ID | The affected item. |
rotate_type | Type of rotation. |
auto_center | Whether to automatically rotate around the selection center. |
center_x | The hor. coordinate of the center of rotation. |
center_y | The vert. coordinate of the center of rotation. |

#### Returns

The rotated item.

Since: 2.8

### gimp_item_transform_rotate ()

    gint32
    gimp_item_transform_rotate (gint32 item_ID,
                                gdouble angle,
                                gboolean auto_center,
                                gdouble center_x,
                                gdouble center_y);

Rotate the specified item about given coordinates through the specified angle.

This function rotates the specified item.

If a selection exists and the item is a drawable, the portion of the drawable which lies under the selection is cut from the drawable and made into a floating selection which is then rotated by the specified amount. If auto_center is set to TRUE, the rotation is around the selection's center. Otherwise, the coordinate of the center point needs to be specified. The return value is the ID of the rotated floating selection.

If there is no selection or the item is not a drawable, the entire item will be rotated around its center if auto_center is set to TRUE, otherwise the coordinate of the center point needs to be specified. Additionally, if the item has its linked flag set to TRUE, all additional items contained in the image which have the linked flag set to TRUE will also be rotated around the same center point. The return value will be equal to the item ID supplied as input.

This procedure is affected by the following context setters: `gimp_context_set_interpolation()`, `gimp_context_set_transform_direction()`, `gimp_context_set_transform_resize()`.

#### Parameters

item_ID | The affected item. |
angle | The angle of rotation (radians). |
auto_center | Whether to automatically rotate around the selection center. |
center_x | The hor. coordinate of the center of rotation. |
center_y | The vert. coordinate of the center of rotation. |

#### Returns

The rotated item.

Since: 2.8

### gimp_item_transform_scale ()

    gint32
    gimp_item_transform_scale (gint32 item_ID,
                               gdouble x0,
                               gdouble y0,
                               gdouble x1,
                               gdouble y1);

Scale the specified item.

This procedure scales the specified item.

The 2 coordinates specify the new locations of the top-left and bottom-roght corners of the original bounding box.

If a selection exists and the item is a drawable, the portion of the drawable which lies under the selection is cut from the drawable and made into a floating selection which is then scaled as specified. The return value is the ID of the scaled floating selection.

If there is no selection or the item is not a drawable, the entire item will be scaled according to the specified coordinates. Additionally, if the item has its linked flag set to TRUE, all additional items contained in the image which have the linked flag set to TRUE will also be scaled the same way. The return value will be equal to the item ID supplied as input.

This procedure is affected by the following context setters: `gimp_context_set_interpolation()`, `gimp_context_set_transform_direction()`, `gimp_context_set_transform_resize()`.

#### Parameters

item_ID | The affected item. |
x0 | The new x coordinate of the upper-left corner of the scaled region. |
y0 | The new y coordinate of the upper-left corner of the scaled region. |
x1 | The new x coordinate of the lower-right corner of the scaled region. |
y1 | The new y coordinate of the lower-right corner of the scaled region. |

#### Returns

The scaled item.

Since: 2.8

### gimp_item_transform_shear ()

    gint32
    gimp_item_transform_shear (gint32 item_ID,
                               GimpOrientationType shear_type,
                               gdouble magnitude);

Shear the specified item about its center by the specified magnitude.

This procedure shears the specified item.

The shear type parameter indicates whether the shear will be applied horizontally or vertically. The magnitude can be either positive or negative and indicates the extent (in pixels) to shear by.

If a selection exists and the item is a drawable, the portion of the drawable which lies under the selection is cut from the drawable and made into a floating selection which is then sheared as specified. The return value is the ID of the sheared floating selection.

If there is no selection or the item is not a drawable, the entire item will be sheared according to the specified parameters. Additionally, if the item has its linked flag set to TRUE, all additional items contained in the image which have the linked flag set to TRUE will also be sheared the same way. The return value will be equal to the item ID supplied as input.

This procedure is affected by the following context setters: `gimp_context_set_interpolation()`, `gimp_context_set_transform_direction()`, `gimp_context_set_transform_resize()`.

#### Parameters

item_ID | The affected item. |
shear_type | Type of shear. |
magnitude | The magnitude of the shear. |

#### Returns

The sheared item.

Since: 2.8

### gimp_item_transform_2d ()

    gint32
    gimp_item_transform_2d (gint32 item_ID,
                            gdouble source_x,
                            gdouble source_y,
                            gdouble scale_x,
                            gdouble scale_y,
                            gdouble angle,
                            gdouble dest_x,
                            gdouble dest_y);

Transform the specified item in 2d.

This procedure transforms the specified item.

The transformation is done by scaling by the x and y scale factors about the point (source_x, source_y), then rotating around the same point, then translating that point to the new position (dest_x, dest_y).

If a selection exists and the item is a drawable, the portion of the drawable which lies under the selection is cut from the drawable and made into a floating selection which is then transformed as specified. The return value is the ID of the transformed floating selection.

If there is no selection or the item is not a drawable, the entire item will be transformed according to the specified parameters. Additionally, if the item has its linked flag set to TRUE, all additional items contained in the image which have the linked flag set to TRUE will also be transformed the same way. The return value will be equal to the item ID supplied as input.

This procedure is affected by the following context setters: `gimp_context_set_interpolation()`, `gimp_context_set_transform_direction()`, `gimp_context_set_transform_resize()`.

#### Parameters

item_ID | The affected item. |
source_x | X coordinate of the transformation center. |
source_y | Y coordinate of the transformation center. |
scale_x | Amount to scale in x direction. |
scale_y | Amount to scale in y direction. |
angle | The angle of rotation (radians). |
dest_x | X coordinate of where the center goes. |
dest_y | Y coordinate of where the center goes. |

#### Returns

The transformed item.

Since: 2.8

### gimp_item_transform_matrix ()

    gint32
    gimp_item_transform_matrix (gint32 item_ID,
                                gdouble coeff_0_0,
                                gdouble coeff_0_1,
                                gdouble coeff_0_2,
                                gdouble coeff_1_0,
                                gdouble coeff_1_1,
                                gdouble coeff_1_2,
                                gdouble coeff_2_0,
                                gdouble coeff_2_1,
                                gdouble coeff_2_2);

Transform the specified item in 2d.

This procedure transforms the specified item.

The transformation is done by assembling a 3x3 matrix from the coefficients passed.

If a selection exists and the item is a drawable, the portion of the drawable which lies under the selection is cut from the drawable and made into a floating selection which is then transformed as specified. The return value is the ID of the transformed floating selection.

If there is no selection or the item is not a drawable, the entire item will be transformed according to the specified matrix. Additionally, if the item has its linked flag set to TRUE, all additional items contained in the image which have the linked flag set to TRUE will also be transformed the same way. The return value will be equal to the item ID supplied as input.

This procedure is affected by the following context setters: `gimp_context_set_interpolation()`, `gimp_context_set_transform_direction()`, `gimp_context_set_transform_resize()`.

#### Parameters

item_ID | The affected item. |
coeff_0_0 | coefficient (0,0) of the transformation matrix. |
coeff_0_1 | coefficient (0,1) of the transformation matrix. |
coeff_0_2 | coefficient (0,2) of the transformation matrix. |
coeff_1_0 | coefficient (1,0) of the transformation matrix. |
coeff_1_1 | coefficient (1,1) of the transformation matrix. |
coeff_1_2 | coefficient (1,2) of the transformation matrix. |
coeff_2_0 | coefficient (2,0) of the transformation matrix. |
coeff_2_1 | coefficient (2,1) of the transformation matrix. |
coeff_2_2 | coefficient (2,2) of the transformation matrix. |

#### Returns

The transformed item.

Since: 2.8