Delivering Responsive Images
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The document discusses the complexities and challenges of implementing responsive images on websites, including the use of the `<picture>` element and various image formats. It highlights the importance of art direction, image breakpoints, and the role of the browser's pre-parser in optimizing image loading for performance. The need for careful selection and management of image sources to improve loading times and avoid excessive markup is also emphasized.
Delivering Responsive Images
- 1. IMAGECON 2017 Delivering Responsive Images Jason Grigsby
- 6. <picture> <!-- 16:9 crop --> <source type="image/webp" media="(min-width: 36em)" srcset="quilt_2/detail/large.webp 1920w, quilt_2/detail/medium.webp 960w, quilt_2/detail/small.webp 480w" /> <source media="(min-width: 36em)" srcset="quilt_2/detail/large.jpg 1920w, quilt_2/detail/medium.jpg 960w, quilt_2/detail/small.jpg 480w" />
- 7. srcset="quilt_2/square/large.webp 822w, quilt_2/square/medium.webp 640w, quilt_2/square/small.webp 320w" /> <source srcset="quilt_2/square/large.jpg 822w, quilt_2/square/medium.jpg 640w, quilt_2/square/small.jpg 320w" /> <img src="quilt_2/detail/medium.jpg" alt="Detail of the above quilt, highlighting the embroidery and exotic stitchwork." /> </picture>
- 8. ”This is way too complex and heavy markup language. Can you imagine yourselves doing that in 300 images in a web site? This will be a nightmare to manage.” ”There are so many things wrong with these new responsive image systems.” “
- 9. background-image: -webkit-linear-gradient( 45deg, rgba(255, 255, 255, .15) 25%, transparent 25%, transparent 50%, rgba(255, 255, 255, .15) 50%, rgba(255, 255, 255, .15) 75%, transparent 75%, transparent); background-image: -o-linear-gradient( 45deg, rgba(255, 255, 255, .15) 25%,
- 10. transparent 75%, transparent); background-image: linear-gradient(45deg, rgba(255, 255, 255, .15) 25%, transparent 25%, transparent 50%, rgba(255, 255, 255, .15) 50%, rgba(255, 255, 255, .15) 75%, transparent 75%, transparent); And that’s why no one uses gradients…
- 11. Images have always been difficult.
- 14. PNG compression 1,498 bytes 1,980 bytes 12,850 bytes
- 17. https://www.flickr.com/photos/whitehouse/8491445521 Resolution Switching Includes high-density (retina) images.
- 24. Art direction: Images with text
- 25. Art direction: Images with text
- 26. Art direction: Images with text
- 29. <img> Icon made by Daniel Bruce from www.flaticon.com is licensed under CC BY 3.0 <picture> <source> srcset media sizes type
- 30. <picture> <source media="(min-width: 650px)" srcset="kitten-large.png"> <source media="(min-width: 465px)" srcset="kitten-medium.png"> <img src="kitten-small.png" alt="a cute kitten"> </picture> All rules are applied to <img> element Original Chrome Team Example: http://googlechrome.github.io/samples/picture-element/
- 31. <img> do you need anything else?
- 32. Fixed width, single density <img> is all you need.
- 36. Small difference in file size or using SVG? <img> is all you need.
- 38. srcset
- 39. display density comma-separated list <img src="cat.jpg" alt="cat" srcset="cat.jpg, cat-2X.jpg 2x">
- 40. Easy so far, right?
- 42. 1849 × 749 – 256K 2x = 3698 × 1498 – 508K
- 43. We need more source files.
- 44. width of the image sources Browser picks best source <img src="cat.jpg" alt="cat" srcset="cat-160.jpg 160w, cat-320.jpg 320w, cat-640.jpg 640w, cat-1280.jpg 1280w">
- 46. Image requested HTML requested CSS and JS requested HTML parsing starts Image requested Image requested Image requested
- 48. CSS evaluation beginning Images are downloaded before size is known The only thing the lookahead pre-parser knows is the size of the viewport.
- 49. <img src="cat.jpg" alt="cat" srcset="cat-160.jpg 160w, cat-320.jpg 320w, cat-640.jpg 640w, cat-1280.jpg 1280w">
- 50. Images are nearly same size as viewport
- 52. Tug of war between responsive images and the lookahead pre-parser.
- 54. https://www.flickr.com/photos/davechiu/24165369 https://www.flickr.com/photos/ostrosky/4149725733 Lookahead pre-parser Know everything in advance. Start downloading immediately. Responsive images Wait until last minute. Know size of image after CSS / JS.
- 55. The pre-parser is why we can’t solve responsive images with CSS, JS or a magical new image format. https://www.flickr.com/photos/hamur0w0/6984884135
- 56. Lookahead Pre-parser Key to a FasterWeb 20% 19% http://andydavies.me/blog/2013/10/22/how-the-browser-pre-loader-makes-pages-load-faster/
- 57. ~43% of image fetches are initiated by the speculative HTML scanner, which account for ~50% of transferred bytes. —Ilya Grigorik “ http://bigqueri.es/t/who-initiates-image-downloads/568
- 59. <img src="cat.jpg" alt="cat" srcset="cat-160.jpg 160w, cat-320.jpg 320w, cat-640.jpg 640w, cat-1280.jpg 1280w" sizes=“max-width(480px) 100vw, max-width(900px) 33vw, 171px”> sizes="(max-width: 480px) 100vw, (max-width: 900px) 33vw, 254px" sizesisrequired wheneversrcsetuses widthdescriptors
- 60. media condition (subset of media queries) length viewport width unit if there is no media condition, then it is the default length length can be absolute, relative or even calc() sizes="(max-width: 480px) 100vw, (max-width: 900px) 33vw, 254px"
- 61. sizes=" (max-width: 480px) 100vw, (max-width: 900px) 33vw, 254px"
- 62. sizes=" (max-width: 480px) 100vw, (max-width: 900px) 33vw, 254px"
- 63. sizes=" (max-width: 480px) 100vw, (max-width: 900px) 33vw, 254px"
- 64. What about separation of content from style?
- 65. Sizes is a necessary compromise: responsive images and speculative downloading
- 66. srcset and sizes let browsers be smarthttps://www.flickr.com/photos/alicejamieson/3164148439
- 67. <picture?>
- 69. <picture> <source media="(min-width: 900px)" srcset="cat-vertical.jpg"> <source media="(min-width: 750px)" srcset="cat-horizontal.jpg"> <img src="cat.jpg" alt="cat"> </picture> media query full srcset multiple <source>s <img>required
- 70. Shopify using <picture> for art direction
- 71. Shopify using <picture> for art direction <picture> <source srcset="homepage-person@desktop.png, homepage-person@desktop-2x.png 2x" media="(min-width: 990px)"> <source srcset="homepage-person@tablet.png, homepage-person@tablet-2x.png 2x" media="(min-width: 750px)"> <img srcset="homepage-person@mobile.png, homepage-person@mobile-2x.png 2x" alt="Shopify Merchant, Corrine Anestopoulos"> </picture> Simplified markup
- 72. another use for <picture> https://www.flickr.com/photos/delete08/4869608487
- 73. declare different types of images unless art direction, you don’t need media attribute <picture> <source type="image/svg+xml" srcset="logo.xml"> <source type="image/webp" srcset="logo.webp"> <img src="logo.png" alt="ACME Corp"> </picture>
- 74. New image formats present new possibilities JPEG 2000 handles alpha channel images well http://www.useragentman.com/blog/2015/01/14/using-webp-jpeg2000-jpegxr-apng-now-with-picturefill-and-modernizr/
- 75. JPEG 2000 19.2K JPEG-XR 95.7K PNG 325.7K Web-P 56K Alpha Channel Dice Image http://www.useragentman.com/blog/2015/01/14/using-webp-jpeg2000-jpegxr-apng-now-with-picturefill-and-modernizr/
- 78. http://www.gratisography.com/ Art direction may dictate image breakpoints
- 79. https://www.flickr.com/photos/photosdavidgabrielfischer/15706338457 Image breakpoints for resolution switching.
- 80. For responsive design breakpoints, resize the browser until the page looks bad then… BOOM! you need a breakpoint.
- 81. 2000 x 3010 761K 200 x 301 15K How many image breakpoints?
- 82. 2000 x 3010 761K 200 x 301 15K Scaled down images don’t look bad.
- 83. 2000 x 3010 250K 400 x 602 Actual size in page 800 x 1204 73K
- 84. 2000 x 3010 250K 400 x 602 Actual size in page 800 x 1204 73K 600 x 903 42K
- 85. 400 x 602 Actual size in page 800 x 1204 73K 600 x 903 42K 500 x 753 31K 450 x 678 27K
- 86. 400 x 602 Actual size in page
- 87. 400 x 602 Actual size in page Is the only intrinsic information we have about image size.
- 88. In the responsive layouts I’ve worked on, content image sizes and their breakpoints were chosen for completely different reasons than the design (CSS) breakpoints: the former for sensible jumps in file size to match screen dimension and/or density, and the latter for how content modules are visibly designed at given viewport dimensions. —Scott Jehl, Filament Group http://lists.w3.org/Archives/Public/public-whatwg-archive/2012May/0613.html “
- 89. What is a sensible jump in file size?
- 90. Images compress differently Both images are 960x660 pixels 151K, JPEG 13K PNG
- 91. Responsive Images Performance Budget
- 92. Source image: 500x333 58K What is the cost of flexible images?
- 93. Source image: 500x333 58K What is the cost of flexible images? Size in page: 300x200 24K Making this image flexible costs 34K.
- 94. What if we set a performance budget of 20K per image for flexible images?
- 95. Width Height File Size 320 213 25K 453 302 44K 579 386 65K 687 458 85K 786 524 104K 885 590 124K 975 650 142K 990 660 151K 8 image breakpoints https://www.flickr.com/photos/lyza/6733380533
- 96. Width Height File Size 320 213 9K 731 487 29K 990 660 40K 3 image breakpoints https://www.flickr.com/photos/lyza/6210160407
- 97. 7 image breakpoints Width Height File Size 320 213 24K 471 314 43K 612 408 64K 728 485 84K 840 560 103K 944 629 122K 990 660 131K https://www.flickr.com/photos/lyza/6167714218
- 98. Width Height File Size 990 660 13K 1 image breakpoint
- 100. Pick representative images and test how many breakpoints you’ll need. Image breakpoints are not a science yet. https://www.flickr.com/photos/ecstaticist/5465673165
- 102. client hints
- 103. displaydensity width of image in page may not be useful GET cat.jpg Accept: image/webp,image/*,*/*;q=0.8 DPR: 2 Viewport-Width: 1024 Width: 508
- 104. <img src="cat.jpg" alt="cat" sizes="(max-width: 480px) 100vw, (max-width: 900px) 33vw, 254px"> srcset="cat-160.jpg 160w, cat-320.jpg 320w, cat-640.jpg 640w, cat-1280.jpg 1280w"
- 105. sizes="(max-width: 480px) 100vw, (max-width: 900px) 33vw, 254px"> <img src="cat.jpg" alt="cat" necessary to calculate image width
- 106. image formats browser understands GET cat.jpg Accept: image/webp,image/*,*/*;q=0.8 DPR: 2 Viewport-Width: 1024 Width: 508
- 107. <picture> <!-- serve WebP to Chrome and Opera --> <source media="(min-width: 50em)" sizes="50vw" srcset="/image/thing-200.webp 200w, /image/thing-400.webp 400w, /image/thing-800.webp 800w, /image/thing-1200.webp 1200w, /image/thing-1600.webp 1600w, /image/thing-2000.webp 2000w" type="image/webp"> <source sizes="(min-width: 30em) 100vw" srcset="/image/thing-crop-200.webp 200w, /image/thing-crop-400.webp 400w, /image/thing-crop-800.webp 800w, /image/thing-crop-1200.webp 1200w, /image/thing-crop-1600.webp 1600w, /image/thing-crop-2000.webp 2000w" type="image/webp"> <!-- serve JPEGXR to Edge --> <source
- 108. /image/thing-crop-1600.jpgxr 1600w, /image/thing-crop-2000.jpgxr 2000w" type="image/vnd.ms-photo"> <!-- serve JPEG to others --> <source media="(min-width: 50em)" sizes="50vw" srcset="/image/thing-200.jpg 200w, /image/thing-400.jpg 400w, /image/thing-800.jpg 800w, /image/thing-1200.jpg 1200w, /image/thing-1600.jpg 1600w, /image/thing-2000.jpg 2000w"> <source sizes="(min-width: 30em) 100vw" srcset="/image/thing-crop-200.jpg 200w, /image/thing-crop-400.jpg 400w, /image/thing-crop-800.jpg 800w, /image/thing-crop-1200.jpg 1200w, /image/thing-crop-1600.jpg 1600w, /image/thing-crop-2000.jpg 2000w"> <!-- fallback for browsers that don't support picture --> <img src="/image/thing.jpg" width="50%"> </picture>
- 109. <picture> <source media="(min-width: 50em)" sizes="50vw" srcset="/image/thing"> <img sizes="100vw" src="/image/thing-crop"> </picture>
- 110. <meta http-equiv="Accept-CH" content="DPR, Viewport-Width, Width"> only declare the hints you need
- 114. Questions to ask about images Where are the source files and what is the process for publishing? Is there a big difference between smallest and largest image size? Resolution switching or art direction? Can we use SVG? Are there representative images we can use to find sensible jumps in file sizes for our image breakpoints? Do we want to support multiple image formats?
- 115. Image Description Format Size Markup Notes Property logos PNG8 (future SVG) Regular, Retina <img> Little variance between the wide and small screen image sizes. Partner logos PNG8 (future SVG) Regular, Retina <img> Little variance between the wide and small screen image sizes. Iconography SVG — <img> — Brand logos PNG8 (future SVG) regular, Retina <img> Assumes little variance between the wide and small screen image sizes. Property photography JPG (conditionalWebP) Dynamically resized and compressed srcset and sizes Templates specify breakpoints. Promo images w/ text (art direction) Whichever is appropriate As many sizes as needed. <picture> Content producer defines images and breakpoints in CMS. Example of images audit for a large site
- 122. https://www.flickr.com/photos/mariachily/5250487136 Responsive images can seem daunting…
- 123. Remember, you’re not alone… https://www.flickr.com/photos/max-design/3751402935
- 125. We will build tools to make the climb easier…
- 126. We merely need to take the first steps. https://www.flickr.com/photos/akras/1477140536
- 129. http://www.gratisography.com/ Special thanks to Simon Pieters, Mat Marquis, Eric Portis,YoavWeiss, and the rest of the RICG. Shout out to all of the amazing photographers who share their work under creative commons.You rule!