update http links

- prefer https

- metadataworkinggroup.org/com seem to be offline; the web archive link
  was obtained from exiftool: https://exiftool.org/TagNames/MWG.html

- fix kramdown link, rubyforge has been gone a long time

- fix png/zlib links

Bug: webp:544
Bug: b/202302177
Change-Id: Id69de4553e7baf00393f12a2c1acb262443a1a93

src/dec/vp8l_dec.c

@@ -84,7 +84,7 @@ static const uint8_t kCodeToPlane[CODE_TO_PLANE_CODES] = {
 // to 256 (green component values) + 24 (length prefix values)
 // + color_cache_size (between 0 and 2048).
 // All values computed for 8-bit first level lookup with Mark Adler's tool:
-// http://www.hdfgroup.org/ftp/lib-external/zlib/zlib-1.2.5/examples/enough.c
+// https://github.com/madler/zlib/blob/v1.2.5/examples/enough.c
 #define FIXED_TABLE_SIZE (630 * 3 + 410)
 static const uint16_t kTableSize[12] = {
   FIXED_TABLE_SIZE + 654,

src/dsp/enc_neon.c

@@ -9,7 +9,7 @@
 //
 // ARM NEON version of speed-critical encoding functions.
 //
-// adapted from libvpx (http://www.webmproject.org/code/)
+// adapted from libvpx (https://www.webmproject.org/code/)
 
 #include "src/dsp/dsp.h"
 

src/dsp/yuv.h

@@ -10,7 +10,7 @@
 // inline YUV<->RGB conversion function
 //
 // The exact naming is Y'CbCr, following the ITU-R BT.601 standard.
-// More information at: http://en.wikipedia.org/wiki/YCbCr
+// More information at: https://en.wikipedia.org/wiki/YCbCr
 // Y = 0.2569 * R + 0.5044 * G + 0.0979 * B + 16
 // U = -0.1483 * R - 0.2911 * G + 0.4394 * B + 128
 // V = 0.4394 * R - 0.3679 * G - 0.0715 * B + 128

src/utils/huffman_encode_utils.c

@@ -161,7 +161,7 @@ static void SetBitDepths(const HuffmanTree* const tree,
 // especially when population counts are longer than 2**tree_limit, but
 // we are not planning to use this with extremely long blocks.
 //
-// See http://en.wikipedia.org/wiki/Huffman_coding
+// See https://en.wikipedia.org/wiki/Huffman_coding
 static void GenerateOptimalTree(const uint32_t* const histogram,
                                 int histogram_size,
                                 HuffmanTree* tree, int tree_depth_limit,

src/utils/quant_levels_dec_utils.c

@@ -30,7 +30,7 @@
 
 #define DFIX 4           // extra precision for ordered dithering
 #define DSIZE 4          // dithering size (must be a power of two)
-// cf. http://en.wikipedia.org/wiki/Ordered_dithering
+// cf. https://en.wikipedia.org/wiki/Ordered_dithering
 static const uint8_t kOrderedDither[DSIZE][DSIZE] = {
   {  0,  8,  2, 10 },     // coefficients are in DFIX fixed-point precision
   { 12,  4, 14,  6 },

src/utils/utils.c

@@ -23,7 +23,7 @@
 // alloc/free etc) is printed. For debugging/tuning purpose only (it's slow,
 // and not multi-thread safe!).
 // An interesting alternative is valgrind's 'massif' tool:
-//    http://valgrind.org/docs/manual/ms-manual.html
+//    https://valgrind.org/docs/manual/ms-manual.html
 // Here is an example command line:
 /*    valgrind --tool=massif --massif-out-file=massif.out \
                --stacks=yes --alloc-fn=WebPSafeMalloc --alloc-fn=WebPSafeCalloc

src/webp/decode.h

@@ -85,7 +85,7 @@ WEBP_EXTERN uint8_t* WebPDecodeBGR(const uint8_t* data, size_t data_size,
 // Upon return, the Y buffer has a stride returned as '*stride', while U and V
 // have a common stride returned as '*uv_stride'.
 // Return NULL in case of error.
-// (*) Also named Y'CbCr. See: http://en.wikipedia.org/wiki/YCbCr
+// (*) Also named Y'CbCr. See: https://en.wikipedia.org/wiki/YCbCr
 WEBP_EXTERN uint8_t* WebPDecodeYUV(const uint8_t* data, size_t data_size,
                                    int* width, int* height,
                                    uint8_t** u, uint8_t** v,