PHP根据输入向上/向下缩放数字?

如果情节 y = 1/-279x + 280/279 反映了你想要什么。

我用Ruby编写了以下脚本,应该很容易翻译成PHP:

require "bundler/inline"

gemfile do
  gem "rspec"
end

require "rspec/autorun"

MAX_SIZE_PERCENTAGE = 1.0

def size_it(text_length, maximum_length)
  alpha = - MAX_SIZE_PERCENTAGE / (maximum_length - MAX_SIZE_PERCENTAGE)
  beta = maximum_length / (maximum_length - MAX_SIZE_PERCENTAGE)
  ((alpha * text_length) + beta).round(2)
end

RSpec.describe "dynamic size calculation" do
  it "100% when minimal size" do
    text_length = 1
    maximum_size = 280
    expect(size_it(text_length, maximum_size)).to eq(1)
  end

  it "75% when almost too short" do
    text_length = 70
    maximum_size = 280
    expect(size_it(text_length, maximum_size)).to eq(0.75)
  end

  it "50% when half point" do
    text_length = 140
    maximum_size = 280
    expect(size_it(text_length, maximum_size)).to eq(0.5)
  end

  it "25% when almost too long" do
    text_length = 210
    maximum_size = 280
    expect(size_it(text_length, maximum_size)).to eq(0.25)
  end

  it "0% when maximum size" do
    text_length = 280
    maximum_size = 280
    expect(size_it(text_length, maximum_size)).to eq(0)
  end
end

数学是直观的,有一些地雷:

• 整数除法,例如1/280导致0而不是0.0003,我通过调用 .to_f ,Ruby的方式来铸造浮动。
• 舍入误差,预期为0.25,实际为0.2503213,我通过调用进行了调整 round(2) ,Ruby四舍五入到最接近的小数点。