Method
VipsImageresize
Declaration [src]
int
vips_resize (
VipsImage* in,
VipsImage** out,
double scale,
...
)
Description [src]
Resize an image.
Set gap to speed up downsizing by having vips_shrink() to shrink
with a box filter first. The bigger gap, the closer the result
to the fair resampling. The smaller gap, the faster resizing.
The default value is 2.0 (very close to fair resampling
while still being faster in many cases).
vips_resize() normally uses VIPS_KERNEL_LANCZOS3 for the final
reduce, you can change this with kernel. Downsizing is done with centre convention.
When upsizing (scale > 1), the operation uses vips_affine() with
a VipsInterpolate selected depending on kernel. It will use
VipsInterpolate “bicubic” for VIPS_KERNEL_CUBIC and above. It
adds a 0.5 pixel displacement to the input pixels to get centre convention scaling.
vips_resize() normally maintains the image aspect ratio. If you set
vscale, that factor is used for the vertical scale and scale for the horizontal.
If either axis would drop below 1px in size, the shrink in that dimension is limited. This breaks the image aspect ratio, but prevents errors due to fractional pixel sizes.
This operation does not change xres or yres. The image resolution needs to be updated by the application.
This operation does not premultiply alpha. If your image has an alpha
channel, you should use vips_premultiply() on it first.
optional arguments
vscale:gdouble, vertical scale factorkernel:VipsKernel, kernel to reduce with (default:VIPS_KERNEL_LANCZOS3)gap:gdouble, reducing gap to use (default: 2.0)
See also
This method is not directly available to language bindings.
Parameters
out-
Type:
VipsImageOutput image.
The argument will be set by the function. The caller of the method takes ownership of the returned data, and is responsible for freeing it. scale-
Type:
doubleScale factor.
...-
Type:
NULL-terminated list of optional named arguments.