[example_web] show loading of an image

Required some redesign of `TextureAllocator` as well as
some improvements to the fetch API.

Cargo.lock

@@ -21,6 +21,12 @@ version = "0.2.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ee2a4ec343196209d6594e19543ae87a39f96d5534d7174822a3ad825dd6ed7e"
 
+[[package]]
+name = "adler32"
+version = "1.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "aae1277d39aeec15cb388266ecc24b11c80469deae6067e17a1a7aa9e5c1f234"
+
 [[package]]
 name = "ahash"
 version = "0.4.6"
@@ -72,7 +78,7 @@ dependencies = [
  "addr2line",
  "cfg-if 1.0.0",
  "libc",
- "miniz_oxide",
+ "miniz_oxide 0.4.3",
  "object",
  "rustc-demangle",
 ]
@@ -107,6 +113,12 @@ version = "3.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2e8c087f005730276d1096a652e92a8bacee2e2472bcc9715a74d2bec38b5820"
 
+[[package]]
+name = "bytemuck"
+version = "1.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "41aa2ec95ca3b5c54cf73c91acf06d24f4495d5f1b1c12506ae3483d646177ac"
+
 [[package]]
 name = "byteorder"
 version = "1.3.4"
@@ -245,6 +257,12 @@ dependencies = [
  "objc",
 ]
 
+[[package]]
+name = "color_quant"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3d7b894f5411737b7867f4827955924d7c254fc9f4d91a6aad6b097804b1018b"
+
 [[package]]
 name = "const_fn"
 version = "0.4.3"
@@ -333,6 +351,15 @@ dependencies = [
  "objc",
 ]
 
+[[package]]
+name = "crc32fast"
+version = "1.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "81156fece84ab6a9f2afdb109ce3ae577e42b1228441eded99bd77f627953b1a"
+dependencies = [
+ "cfg-if 1.0.0",
+]
+
 [[package]]
 name = "criterion"
 version = "0.3.3"
@@ -473,6 +500,16 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "deflate"
+version = "0.8.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "73770f8e1fe7d64df17ca66ad28994a0a623ea497fa69486e14984e715c5d174"
+dependencies = [
+ "adler32",
+ "byteorder",
+]
+
 [[package]]
 name = "demo_glium"
 version = "0.1.0"
@@ -586,6 +623,7 @@ version = "0.1.0"
 dependencies = [
  "egui",
  "egui_web",
+ "image",
  "js-sys",
  "serde",
  "serde_json",
@@ -755,6 +793,22 @@ version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b9e0384b61958566e926dc50660321d12159025e767c18e043daf26b70104c39"
 
+[[package]]
+name = "image"
+version = "0.23.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b4f0a8345b33b082aedec2f4d7d4a926b845cee184cbe78b703413066564431b"
+dependencies = [
+ "bytemuck",
+ "byteorder",
+ "color_quant",
+ "jpeg-decoder",
+ "num-iter",
+ "num-rational",
+ "num-traits",
+ "png",
+]
+
 [[package]]
 name = "instant"
 version = "0.1.8"
@@ -794,6 +848,15 @@ version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8eaf4bc02d17cbdd7ff4c7438cafcdf7fb9a4613313ad11b4f8fefe7d3fa0130"
 
+[[package]]
+name = "jpeg-decoder"
+version = "0.1.20"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cc797adac5f083b8ff0ca6f6294a999393d76e197c36488e2ef732c4715f6fa3"
+dependencies = [
+ "byteorder",
+]
+
 [[package]]
 name = "js-sys"
 version = "0.3.45"
@@ -905,6 +968,15 @@ dependencies = [
  "autocfg",
 ]
 
+[[package]]
+name = "miniz_oxide"
+version = "0.3.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "791daaae1ed6889560f8c4359194f56648355540573244a5448a83ba1ecc7435"
+dependencies = [
+ "adler32",
+]
+
 [[package]]
 name = "miniz_oxide"
 version = "0.4.3"
@@ -1046,6 +1118,28 @@ dependencies = [
  "num-traits",
 ]
 
+[[package]]
+name = "num-iter"
+version = "0.1.42"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b2021c8337a54d21aca0d59a92577a029af9431cb59b909b03252b9c164fad59"
+dependencies = [
+ "autocfg",
+ "num-integer",
+ "num-traits",
+]
+
+[[package]]
+name = "num-rational"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "12ac428b1cb17fce6f731001d307d351ec70a6d202fc2e60f7d4c5e42d8f4f07"
+dependencies = [
+ "autocfg",
+ "num-integer",
+ "num-traits",
+]
+
 [[package]]
 name = "num-traits"
 version = "0.2.14"
@@ -1202,6 +1296,18 @@ dependencies = [
  "web-sys",
 ]
 
+[[package]]
+name = "png"
+version = "0.16.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dfe7f9f1c730833200b134370e1d5098964231af8450bce9b78ee3ab5278b970"
+dependencies = [
+ "bitflags",
+ "crc32fast",
+ "deflate",
+ "miniz_oxide 0.3.7",
+]
+
 [[package]]
 name = "proc-macro-crate"
 version = "0.1.5"