Foreword

All the functions described in this page are used to add a bias to LqrCarver objects. A positive biased pixel will be more likely to be avoided by seams, and thus be preserved during rescaling, while a negative bias has the opposite effect.

All of these functions must be called before lqr_carver_resize(3). If called multiple times, the biases added at each call will sum up.

Adding a bias pixel by pixel

The function lqr_carver_bias_add_xy adds a bias to the x, y pixel of the image loaded into the LqrCarver object pointed to by carver

A typical value for bias_factor would be 1000 (in absolute value).

Adding a bias from a buffer

The function lqr_carver_bias_add_area adds a bias to an area of the image loaded into the LqrCarver object pointed to by carver.

The parameter buffer must point to an array of doubles of size width * height, ordered first by rows, then by columns.

The offset of the area relative to the image can be specified through x_off and y_off. The bias area can exceed the boundary of the image, and the offsets can be negative.

The parameter bias_factor is an overall bias scale. A typical value when the buffer contents are of the order of 1 would be 1000 (in absolute value).

The function lqr_carver_bias_add can be used when the area to add is of the same size of the image loaded in the LqrCarver object and the offsets are 0.

Adding a bias from an image

The functions lqr_carver_bias_add_rgb_area and lqr_carver_bias_add_rgb are very similar to lqr_carver_bias_add_area and lqr_carver_bias_add, except that they use 8-bit multi-channel images as inputs.

The number of channels in the image is passed via the parameter channels. The last channel is assumed to be the alpha (opacity) channel if channels is equal to 2 or greater than 3 (if this is not the case, use the previous functions).

The bias is computed from the average of the colour channels, multiplied by the value of the alpha channel if present. For example, in RGBA images a white, nontransparent pixel is equivalent to a value of 1.0 when using a buffer in lqr_carver_bias_add_area.

Return values

The return values follow the Liquid Rescale library signalling system.

See also

LqrRetVal(3), lqr_carver_init(3), lqr_carver_rigmask_add(3)