WebP support

[ishitatsuyuki]

While WebP is only supported by Chrome, its dominance of market means that about 70% of the users will able to load that format.

WebP is a good compromise between JPEG and PNG, in terms that it can perform lossy compression while not destroying alpha properties. It simply compresses better, too.

[piranha]

Also any mobile app can implement WebP support, which makes it even more worthwhile.

[polarathene]

Firefox released version 65 early 2019, now providing WebP support too.

[teacoat]

Agreed, browser support is good enough and the benefits plenty, please support!

[lilith]

libwebp is 1.0 now, so we can support it.

[kepi]

Are there any news about WebP support?

[lilith]

Not yet, although we had a big breakthrough today that should free up more dev effort towards webp and rewriting the webserver.

[kornelski]

I'm maintaining bindings if you need them: https://lib.rs/crates/libwebp-sys

[lilith]

@kornelski Perfect! I'll use those. Do you have any suggestions for output tuning or presets? The array of options seems dizzying.

struct WebPConfig {
  int lossless;           // Lossless encoding (0=lossy(default), 1=lossless).
  float quality;          // between 0 and 100. For lossy, 0 gives the smallest
                          // size and 100 the largest. For lossless, this
                          // parameter is the amount of effort put into the
                          // compression: 0 is the fastest but gives larger
                          // files compared to the slowest, but best, 100.
  int method;             // quality/speed trade-off (0=fast, 6=slower-better)

  WebPImageHint image_hint;  // Hint for image type (lossless only for now).

  // Parameters related to lossy compression only:
  int target_size;        // if non-zero, set the desired target size in bytes.
                          // Takes precedence over the 'compression' parameter.
  float target_PSNR;      // if non-zero, specifies the minimal distortion to
                          // try to achieve. Takes precedence over target_size.
  int segments;           // maximum number of segments to use, in [1..4]
  int sns_strength;       // Spatial Noise Shaping. 0=off, 100=maximum.
  int filter_strength;    // range: [0 = off .. 100 = strongest]
  int filter_sharpness;   // range: [0 = off .. 7 = least sharp]
  int filter_type;        // filtering type: 0 = simple, 1 = strong (only used
                          // if filter_strength > 0 or autofilter > 0)
  int autofilter;         // Auto adjust filter's strength [0 = off, 1 = on]
  int alpha_compression;  // Algorithm for encoding the alpha plane (0 = none,
                          // 1 = compressed with WebP lossless). Default is 1.
  int alpha_filtering;    // Predictive filtering method for alpha plane.
                          //  0: none, 1: fast, 2: best. Default if 1.
  int alpha_quality;      // Between 0 (smallest size) and 100 (lossless).
                          // Default is 100.
  int pass;               // number of entropy-analysis passes (in [1..10]).

  int show_compressed;    // if true, export the compressed picture back.
                          // In-loop filtering is not applied.
  int preprocessing;      // preprocessing filter (0=none, 1=segment-smooth)
  int partitions;         // log2(number of token partitions) in [0..3]
                          // Default is set to 0 for easier progressive decoding.
  int partition_limit;    // quality degradation allowed to fit the 512k limit on
                          // prediction modes coding (0: no degradation,
                          // 100: maximum possible degradation).
  int use_sharp_yuv;      // if needed, use sharp (and slow) RGB->YUV conversion
};

[kornelski]

I haven't looked into tuning these options yet.

[lilith]

Thanks! I've just used the simple encoder API for now.

WebP support can be activated using the webplossy {quality} and webplossless encoder presets or using &format=webp&webp.quality=x or &format=webp&webp.lossless=true respectively.

This is in master.

[lilith]

Update: you now use &webp.lossless=true|false and &webp.quality=0..100 to adjust compression rather than reusing the jpeg quality command.