我正在使用Vips通过Shrine调整图像大小，希望可以使用Vips库在图像顶部合并一层文本。
ImageProcessing::Vips.source(image).resize_to_fill!(width,height)
这段代码很好用，如何在resize_to_fill之后添加一层文本？
目标是用白色文字写“ Hello world”，并在图像的中心带有CSS文字阴影。
我尝试编写类似这样的内容，但到目前为止我只得到错误提示：
Vips\Image::text('Hello world!',['font' => 'sans 120','width' => $image->width - 100]);
您的示例看起来像PHP –在Ruby中，您将编写如下内容：
text = Vips::Image.text 'Hello world!',font: 'sans 120',width: image.width - 100
我为您制作了一个演示
#!/usr/bin/ruby
require "vips"
image = Vips::Image.new_from_file ARGV[0],access: :sequential
text_colour = [255,128,128]
shadow_colour = [128,255,128]
h_shadow = 2
v_shadow = 5
blur_radius = 10
# position to render the top-left of the text
text_left = 100
text_top = 200
# render some text ... this will make a one-band uchar image,with 0
# for black,255 for white and intermediate values for anti-aliasing
text_mask = Vips::Image.text "Hello world!",dpi: 300
# we need to enlarge the text mask before we blur so that the soft edges
# don't get clipped
shadow_mask = text_mask.embed(blur_radius,blur_radius,text_mask.width + 2 * blur_radius,text_mask.height + 2 * blur_radius)
# gaussblur() takes sigma as a parameter -- approximate as radius / 2
shadow_mask = blur_radius > 0.1 ?
shadow_mask.gaussblur(blur_radius / 2) : shadow_mask
# make an RGB image the size of the text mask with each pixel set to the
# constant,then attach the text mask as the alpha
rgb = text_mask.new_from_image(text_colour).copy(interpretation: "srgb")
text = rgb.bandjoin(text_mask)
rgb = shadow_mask.new_from_image(shadow_colour).copy(interpretation: "srgb")
shadow = rgb.bandjoin(shadow_mask)
# composite the three layers together
image = image.composite([shadow,text],"over",x: [text_left + h_shadow,text_left],y: [text_top + v_shadow,text_top])
image.write_to_file ARGV[1]
像这样运行：
$ ./try319.rb ~/pics/PNG_transparency_demonstration_1.png x.png
制作：
