server, post: add about images for social media

Signed-off-by: Naman Sood <mail@nsood.in>

fonts/OFL.txt

@@ -0,0 +1,93 @@
+Copyright 2014 The Nunito Project Authors (https://github.com/googlefonts/nunito)
+
+This Font Software is licensed under the SIL Open Font License, Version 1.1.
+This license is copied below, and is also available with a FAQ at:
+http://scripts.sil.org/OFL
+
+
+-----------------------------------------------------------
+SIL OPEN FONT LICENSE Version 1.1 - 26 February 2007
+-----------------------------------------------------------
+
+PREAMBLE
+The goals of the Open Font License (OFL) are to stimulate worldwide
+development of collaborative font projects, to support the font creation
+efforts of academic and linguistic communities, and to provide a free and
+open framework in which fonts may be shared and improved in partnership
+with others.
+
+The OFL allows the licensed fonts to be used, studied, modified and
+redistributed freely as long as they are not sold by themselves. The
+fonts, including any derivative works, can be bundled, embedded, 
+redistributed and/or sold with any software provided that any reserved
+names are not used by derivative works. The fonts and derivatives,
+however, cannot be released under any other type of license. The
+requirement for fonts to remain under this license does not apply
+to any document created using the fonts or their derivatives.
+
+DEFINITIONS
+"Font Software" refers to the set of files released by the Copyright
+Holder(s) under this license and clearly marked as such. This may
+include source files, build scripts and documentation.
+
+"Reserved Font Name" refers to any names specified as such after the
+copyright statement(s).
+
+"Original Version" refers to the collection of Font Software components as
+distributed by the Copyright Holder(s).
+
+"Modified Version" refers to any derivative made by adding to, deleting,
+or substituting -- in part or in whole -- any of the components of the
+Original Version, by changing formats or by porting the Font Software to a
+new environment.
+
+"Author" refers to any designer, engineer, programmer, technical
+writer or other person who contributed to the Font Software.
+
+PERMISSION & CONDITIONS
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of the Font Software, to use, study, copy, merge, embed, modify,
+redistribute, and sell modified and unmodified copies of the Font
+Software, subject to the following conditions:
+
+1) Neither the Font Software nor any of its individual components,
+in Original or Modified Versions, may be sold by itself.
+
+2) Original or Modified Versions of the Font Software may be bundled,
+redistributed and/or sold with any software, provided that each copy
+contains the above copyright notice and this license. These can be
+included either as stand-alone text files, human-readable headers or
+in the appropriate machine-readable metadata fields within text or
+binary files as long as those fields can be easily viewed by the user.
+
+3) No Modified Version of the Font Software may use the Reserved Font
+Name(s) unless explicit written permission is granted by the corresponding
+Copyright Holder. This restriction only applies to the primary font name as
+presented to the users.
+
+4) The name(s) of the Copyright Holder(s) or the Author(s) of the Font
+Software shall not be used to promote, endorse or advertise any
+Modified Version, except to acknowledge the contribution(s) of the
+Copyright Holder(s) and the Author(s) or with their explicit written
+permission.
+
+5) The Font Software, modified or unmodified, in part or in whole,
+must be distributed entirely under this license, and must not be
+distributed under any other license. The requirement for fonts to
+remain under this license does not apply to any document created
+using the Font Software.
+
+TERMINATION
+This license becomes null and void if any of the above conditions are
+not met.
+
+DISCLAIMER
+THE FONT SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
+OF COPYRIGHT, PATENT, TRADEMARK, OR OTHER RIGHT. IN NO EVENT SHALL THE
+COPYRIGHT HOLDER BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+INCLUDING ANY GENERAL, SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL
+DAMAGES, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF THE USE OR INABILITY TO USE THE FONT SOFTWARE OR FROM
+OTHER DEALINGS IN THE FONT SOFTWARE.

go.mod

@@ -4,12 +4,15 @@ go 1.15
 
 require (
 	github.com/aymerick/raymond v2.0.2+incompatible
+	github.com/fogleman/gg v1.3.0 // indirect
+	github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0 // indirect
 	github.com/mitchellh/mapstructure v1.4.1
 	github.com/rjeczalik/notify v0.9.2
 	github.com/wellington/go-libsass v0.9.2
 	github.com/yuin/goldmark v1.3.1
 	github.com/yuin/goldmark-highlighting v0.0.0-20200307114337-60d527fdb691
 	github.com/yuin/goldmark-meta v1.0.0
+	golang.org/x/image v0.0.0-20210628002857-a66eb6448b8d // indirect
 	golang.org/x/net v0.0.0-20210119194325-5f4716e94777 // indirect
 	golang.org/x/sys v0.0.0-20210228012217-479acdf4ea46 // indirect
 )

go.sum

@@ -23,6 +23,10 @@ github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSs
 github.com/dlclark/regexp2 v1.1.6/go.mod h1:2pZnwuY/m+8K6iRw6wQdMtk+rH5tNGR1i55kozfMjCc=
 github.com/dlclark/regexp2 v1.2.0 h1:8sAhBGEM0dRWogWqWyQeIJnxjWO6oIjl8FKqREDsGfk=
 github.com/dlclark/regexp2 v1.2.0/go.mod h1:2pZnwuY/m+8K6iRw6wQdMtk+rH5tNGR1i55kozfMjCc=
+github.com/fogleman/gg v1.3.0 h1:/7zJX8F6AaYQc57WQCyN9cAIz+4bCJGO9B+dyW29am8=
+github.com/fogleman/gg v1.3.0/go.mod h1:R/bRT+9gY/C5z7JzPU0zXsXHKM4/ayA+zqcVNZzPa1k=
+github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0 h1:DACJavvAHhabrF08vX0COfcOBJRhZ8lUbR+ZWIs0Y5g=
+github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0/go.mod h1:E/TSTwGwJL78qG/PmXZO1EjYhfJinVAhrmmHX6Z8B9k=
 github.com/gorilla/csrf v1.6.0/go.mod h1:7tSf8kmjNYr7IWDCYhd3U8Ck34iQ/Yw5CJu7bAkHEGI=
 github.com/gorilla/handlers v1.4.1/go.mod h1:Qkdc/uu4tH4g6mTK6auzZ766c4CA0Ng8+o/OAirnOIQ=
 github.com/gorilla/mux v1.7.3/go.mod h1:1lud6UwP+6orDFRuTfBEV8e9/aOM/c4fVVCaMa2zaAs=
@@ -60,6 +64,8 @@ github.com/yuin/goldmark-highlighting v0.0.0-20200307114337-60d527fdb691 h1:VWSx
 github.com/yuin/goldmark-highlighting v0.0.0-20200307114337-60d527fdb691/go.mod h1:YLF3kDffRfUH/bTxOxHhV6lxwIB3Vfj91rEwNMS9MXo=
 github.com/yuin/goldmark-meta v1.0.0 h1:ScsatUIT2gFS6azqzLGUjgOnELsBOxMXerM3ogdJhAM=
 github.com/yuin/goldmark-meta v1.0.0/go.mod h1:zsNNOrZ4nLuyHAJeLQEZcQat8dm70SmB2kHbls092Gc=
+golang.org/x/image v0.0.0-20210628002857-a66eb6448b8d h1:RNPAfi2nHY7C2srAV8A49jpsYr0ADedCk1wq6fTMTvs=
+golang.org/x/image v0.0.0-20210628002857-a66eb6448b8d/go.mod h1:023OzeP/+EPmXeapQh35lcL3II3LrY8Ic+EFFKVhULM=
 golang.org/x/net v0.0.0-20210119194325-5f4716e94777 h1:003p0dJM77cxMSyCPFphvZf/Y5/NXf5fzg6ufd1/Oew=
 golang.org/x/net v0.0.0-20210119194325-5f4716e94777/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
 golang.org/x/sys v0.0.0-20180926160741-c2ed4eda69e7/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
@@ -69,6 +75,7 @@ golang.org/x/sys v0.0.0-20210228012217-479acdf4ea46 h1:V066+OYJ66oTjnhm4Yrn7SXIw
 golang.org/x/sys v0.0.0-20210228012217-479acdf4ea46/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
 golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
+golang.org/x/text v0.3.6/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=

post.go

@@ -31,6 +31,7 @@ type Post struct {
 	Slug     string
 	Metadata Metadata
 	Contents string
+	Image    bytes.Buffer
 }
 
 func newPost(slug string) (*Post, error) {
@@ -73,6 +74,12 @@ func newPost(slug string) (*Post, error) {
 		Contents: converted.String(),
 	}
 
+	url := blogURL + "/" + slug
+	err = createImage(post.Metadata.Title, post.Metadata.Summary, url, &post.Image)
+	if err != nil {
+		return nil, fmt.Errorf("could not create post image: %v", err)
+	}
+
 	return post, nil
 }
 

server.go

@@ -1,12 +1,22 @@
 package main
 
 import (
+	"bytes"
+	"io"
 	"log"
+	"math"
 	"net/http"
 	"strings"
 	"sync"
 
 	"github.com/aymerick/raymond"
+	"github.com/fogleman/gg"
+)
+
+const (
+	blogTitle   = "Prose"
+	blogURL     = "https://prose.nsood.in"
+	blogSummary = "Where I infodump in Markdown and nobody can stop me."
 )
 
 type server struct {
@@ -16,6 +26,7 @@ type server struct {
 	templates map[string]*raymond.Template
 	postList
 	styles    map[string]string
+	homeImage bytes.Buffer
 }
 
 func newServer() (*server, error) {
@@ -23,6 +34,11 @@ func newServer() (*server, error) {
 		staticHandler: http.FileServer(http.Dir("static/")),
 	}
 
+	err := createImage(blogTitle, blogSummary, blogURL, &s.homeImage)
+	if err != nil {
+		return nil, err
+	}
+
 	posts, err := newPostList()
 	if err != nil {
 		return nil, err
@@ -92,11 +108,18 @@ func (s *server) router(res http.ResponseWriter, req *http.Request) {
 		s.homePage(res, req)
 		return
 	}
+	if slug == "about.png" {
+		s.renderImage(res, req, &s.homeImage)
+		return
+	}
 
 	for _, p := range s.postList {
-		if p.Slug == slug {
+		if slug == p.Slug {
 			s.postPage(p, res, req)
 			return
+		} else if slug == p.Slug+"/about.png" {
+			s.renderImage(res, req, &p.Image)
+			return
 		}
 	}
 
@@ -152,7 +175,7 @@ func (s *server) homePage(res http.ResponseWriter, req *http.Request) {
 		posts = posts + summary
 	}
 
-	page, err := s.createWebPage("Home", "Where I infodump in Markdown and nobody can stop me.", posts)
+	page, err := s.createWebPage("Home", blogSummary, posts)
 
 	if err != nil {
 		s.errorInRequest(res, req, err)
@@ -161,6 +184,14 @@ func (s *server) homePage(res http.ResponseWriter, req *http.Request) {
 	res.Write([]byte(page))
 }
 
+func (s *server) renderImage(res http.ResponseWriter, req *http.Request, img io.Reader) {
+	res.Header().Add("content-type", "image/png")
+	_, err := io.Copy(res, img)
+	if err != nil {
+		s.errorInRequest(res, req, err)
+	}
+}
+
 func (s *server) loadStylesheet(res http.ResponseWriter, req *http.Request, filename string) (ok bool) {
 	contents, ok := s.styles[filename]
 	if !ok {
@@ -170,3 +201,74 @@ func (s *server) loadStylesheet(res http.ResponseWriter, req *http.Request, file
 	res.Write([]byte(contents))
 	return ok
 }
+
+func createImage(title, summary, url string, out io.Writer) error {
+	imgWidth, imgPaddingX, imgPaddingY := 800, 30, 60
+	titleSize, summarySize, urlSize := 42.0, 28.0, 18.0
+	lineHeight := 1.5
+	textWidth := float64(imgWidth - 2*imgPaddingX)
+
+	// temporarily set height = 0 for context only used to generate
+	// wrapped strings
+	draw := gg.NewContext(imgWidth, 0)
+
+	titleFont, err := gg.LoadFontFace("fonts/Nunito-Bold.ttf", titleSize)
+	if err != nil {
+		return err
+	}
+	summaryFont, err := gg.LoadFontFace("fonts/Nunito-LightItalic.ttf", summarySize)
+	if err != nil {
+		return err
+	}
+	urlFont, err := gg.LoadFontFace("fonts/JetBrainsMono-ExtraLight.ttf", urlSize)
+	if err != nil {
+		return err
+	}
+
+	draw.SetFontFace(titleFont)
+	wrappedTitle := draw.WordWrap(title, textWidth)
+	draw.SetFontFace(summaryFont)
+	wrappedSummary := draw.WordWrap(summary, textWidth)
+
+	imgHeight := 2 * imgPaddingY
+	for range wrappedTitle {
+		imgHeight += int(math.Ceil(lineHeight * titleSize))
+	}
+	for range wrappedSummary {
+		imgHeight += int(math.Ceil(lineHeight * summarySize))
+	}
+	imgHeight += int(math.Ceil(lineHeight * urlSize))
+
+	// actual context with actual height
+	draw = gg.NewContext(imgWidth, imgHeight)
+	draw.SetHexColor("#fff")
+	draw.DrawRectangle(0, 0, float64(imgWidth), float64(imgHeight))
+	draw.Fill()
+	draw.SetHexColor("#3498db")
+	accentHeight := 5.0
+	draw.DrawRectangle(0, float64(imgHeight)-accentHeight, float64(imgWidth), accentHeight)
+	draw.Fill()
+
+	offset := float64(imgPaddingY)
+
+	draw.SetFontFace(titleFont)
+	draw.SetHexColor("#333")
+	for _, line := range wrappedTitle {
+		draw.DrawString(line, float64(imgPaddingX), offset)
+		offset += lineHeight * titleSize
+	}
+
+	draw.SetFontFace(summaryFont)
+	draw.SetHexColor("#999")
+	for _, line := range wrappedSummary {
+		draw.DrawString(line, float64(imgPaddingX), offset)
+		offset += lineHeight * summarySize
+	}
+
+	draw.SetHexColor("#333")
+	draw.SetFontFace(urlFont)
+	urlY := float64(imgHeight - imgPaddingY)
+	draw.DrawStringWrapped(url, float64(imgPaddingX), urlY, 0, 0, textWidth, lineHeight, gg.AlignRight)
+
+	return draw.EncodePNG(out)
+}

templates/page.html

@@ -8,6 +8,7 @@
 	<meta property="og:type" content="website">
 	<meta property="og:title" content="{{title}} – Prose">
 	<meta property="og:description" content="{{subtitle}}">
+	<meta property="og:image" content="./about.png">
 	<meta name="twitter:creator" content="@tendstofortytwo">
 	<meta name="color-scheme" content="dark light">
 	<meta name="viewport" content="width=device-width">