github.com/neohugo/neohugo@v0.123.8/resources/images/padding.go (about)

     1  // Copyright 2024 The Hugo Authors. All rights reserved.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  // http://www.apache.org/licenses/LICENSE-2.0
     7  //
     8  // Unless required by applicable law or agreed to in writing, software
     9  // distributed under the License is distributed on an "AS IS" BASIS,
    10  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    11  // See the License for the specific language governing permissions and
    12  // limitations under the License.
    13  
    14  package images
    15  
    16  import (
    17  	"image"
    18  	"image/color"
    19  	"image/draw"
    20  
    21  	"github.com/disintegration/gift"
    22  )
    23  
    24  var _ gift.Filter = (*paddingFilter)(nil)
    25  
    26  type paddingFilter struct {
    27  	top, right, bottom, left int
    28  	ccolor                   color.Color // canvas color
    29  }
    30  
    31  func (f paddingFilter) Draw(dst draw.Image, src image.Image, options *gift.Options) {
    32  	w := src.Bounds().Dx() + f.left + f.right
    33  	h := src.Bounds().Dy() + f.top + f.bottom
    34  
    35  	if w < 1 {
    36  		panic("final image width will be less than 1 pixel: check padding values")
    37  	}
    38  	if h < 1 {
    39  		panic("final image height will be less than 1 pixel: check padding values")
    40  	}
    41  
    42  	i := image.NewRGBA(image.Rect(0, 0, w, h))
    43  	draw.Draw(i, i.Bounds(), image.NewUniform(f.ccolor), image.Point{}, draw.Src)
    44  	gift.New().Draw(dst, i)
    45  	gift.New().DrawAt(dst, src, image.Pt(f.left, f.top), gift.OverOperator)
    46  }
    47  
    48  func (f paddingFilter) Bounds(srcBounds image.Rectangle) image.Rectangle {
    49  	return image.Rect(0, 0, srcBounds.Dx()+f.left+f.right, srcBounds.Dy()+f.top+f.bottom)
    50  }