Is WordPress API visible from PHP file called in htaccess

The .htaccess is parsed before WordPress is loaded, so you don’t get access to WordPress data.

You can make the redirect in WordPress, in a plugin: Hook into 404_template and inspect $_SERVER['REQUEST_URI'] with parse_url(). You should be able to find the matching post for the image then.
You did not write how the permalinks for these posts are built, so we cannot offer a more specific solution.

Related Posts:

  1. Server (WordPress) redirects files that are not supposed to (using htaccess)
  2. Alias ‘wp-content’ directory to something shorter (framework?)
  3. add_rewrite_rule fro html to another url not working
  4. Wildcard forward all posts and pages with few exceptions
  5. Clash of the rewrites
  6. Will references to ugly links automatically redirect to their pretty url permalink?
  7. Hijacking the URL for filtering
  8. WP Login forms action URLs displayed as pretty URLs in browser (ex with Restore Password)
  9. custom htaccess rewrite rule for page
  10. Dynamic URL, not a physical page within the database
  11. Redirecting all old links from previous EE site to new WP site in one go?
  12. Prevent WordPress from automatically correcting URLs
  13. Display content according to current URL
  14. Rewrite WordPress Custom URL
  15. Custom rewrite rule
  16. WordPress .htaccess – route other URLs to another app
  17. Is there a ‘rake routes’ for wordpress?
  18. Changing RSS feed URL structure
  19. Double domain name in category URL-s
  20. Preserve Domain Alias
  21. WordPress redirects non-existing url to existing ones – how to disable
  22. Rewrite Preview URL to include index.php
  23. How to disable URL rewriting for specific URLs?
  24. How do I display only the parent page in the url
  25. How to remove wordpress directory slash
  26. React Router with WordPress
  27. How to redirect large amount of URLs?
  28. Redirecting /px/?q=x to /px/x/
  29. URL redirect on updating the post date
  30. Rewrite vs Redirect from ?p={ID}
  31. Redirect htaccess [closed]
  32. 301 Rewriting htaccess
  33. 404 redirect based on url
  34. How to customize sub-URLs in a wordpress website (.htaccess)
  35. WordPress is adding “category” word before my actual category name in url (and this is unsolicited)
  36. Multiple permalink with and without category for same post
  37. Fresh install redirects to www, breaking page loads
  38. Rewrite URL to get rid of wp-content etc and change URL
  39. taxonomy term in URL slug won’t forward to the correct term for custom post like it does for default categories/normal posts
  40. How to create short urls for sharing and downloadable content?
  41. Redirect A URL Pattern In WordPress Using .htaccess
  42. Migration from old CMS to WordPress 301 redirection rules?
  43. Changes done to .htaccess are not getting reverted back
  44. Does WordPress keep track of a post’s URL history and provide automatic redirects?
  45. Masking wp-content/themes/name/images to just images directory using htaccess
  46. Use subdomain for certain urls
  47. Custom slug in front of search URL
  48. Display posts with author in the url with custom post types
  49. Redirecting WordPress /.htaccess / HSTS / SSL
  50. How to change default page slug?
  51. How to append a URL parameter to all outbound URLs
  52. Appending numbers to url do not break the link
  53. Custom rewrite rules are sending everything to index.php
  54. Sub domain redirection to taxonomy
  55. How to? Redirect /category/sci-fi/ to /category/scifi/?
  56. How to change page URLs to “www.site.com/page” instead of “example.com/blog/page” but keep post URLs as “example.com/blog/post”?
  57. Auto 301 to full post permalink? (using /posts/%post_id%/%postname%)
  58. Add_query_arg + two times the same argument?
  59. WordPress 404 unless there is a space in url
  60. Two “.htaccess” Files Located in Different Directories?
  61. Migrating a page to be an article
  62. How to get “extended” path info from URL in a plugin
  63. Home page with Polylang redirects to other page [closed]
  64. expecting 404 but redirecting to post with url subdirectory in post title
  65. Define orderby in url
  66. hard flush_rewrite_rules() not regenerating .htaccess
  67. Redirect home to another page with htaccess
  68. WordPress Redirecting Non Category Pages /page/nnn to their Canonical URLs
  69. How to building pretty URLs to reflect category hierarchy?
  70. Can I change default registration link (without htaccess)?
  71. A clean custom rewrite rule for weekly archives
  72. Add language prefix to permalinks
  73. URL masking of subdomain to main domain using .htaccess
  74. How to change the Author Slug from Username to Nickname and deal with Special Characters
  75. Per Page Permalink Structure for Page Post Type
  76. Customise particular RSS permalink
  77. RSS feed rewrite matching wrong rule
  78. Rewrite /category/cars into /topics/cars
  79. URL renaming issue
  80. Weird characters behind every single link and images
  81. How do I make WordPress revise an .htaccess file a certain way?
  82. How are rewrite rules applied in WordPress?
  83. Redirect users with “.” (dot) in their username and replace with “-” (dash) to correct profile
  84. Rewrite htacess rule doesn’t work
  85. Allowing multiple URLs for same Post
  86. How to create dynamic URLs on WordPress?
  87. Translatepress taxonomy and custom post type root FIX
  88. Param causing 404
  89. Rewrite Url using .htaccess or hook
  90. WordPress Category url redirects to subdomain
  91. Error 404 wordpress redirecting URL
  92. Remove Page Slug from URL
  93. How to stop WordPress creating URLs that don’t exist
  94. Stop wordpress to redirecting home page if no page found
  95. Rename page URL
  96. how to rewrite folder name in url to another name
  97. Lost WordPress website access after changing URL [closed]
  98. Spurious URL structure (Adding extra /0/s)
  99. WP-Include rewrite directory
  100. WordPress is adding pagination for all pages like www.example.com/page/123. How to remove that?