Add support for displaying correct colors with PNG files that contain embedded ICC color profiles

.github/workflows/ci.py

@@ -36,7 +36,7 @@ def install_deps():
         run('sudo apt-get update')
         run('sudo apt-get install -y libgl1-mesa-dev libxi-dev libxrandr-dev libxinerama-dev'
             ' libxcursor-dev libxcb-xkb-dev libdbus-1-dev libxkbcommon-dev libharfbuzz-dev'
-            ' libpng-dev libfontconfig-dev libxkbcommon-x11-dev libcanberra-dev')
+            ' libpng-dev liblcms2-dev libfontconfig-dev libxkbcommon-x11-dev libcanberra-dev')
     if is_bundle:
         install_bundle()
     else:

bypy/linux/__main__.py

@@ -26,7 +26,7 @@ kitty_constants = iv['kitty_constants']
 
 def binary_includes():
     return tuple(map(get_dll_path, (
-            'expat', 'sqlite3', 'ffi', 'z', 'lzma', 'png16',
+            'expat', 'sqlite3', 'ffi', 'z', 'lzma', 'png16', 'lcms2',
 
             # dont include freetype because fontconfig is closely coupled to it
             # and also distros often patch freetype

bypy/macos/__main__.py

@@ -262,6 +262,7 @@ class Freeze(object):
                 'z.1',
                 'harfbuzz.0',
                 'png16.16',
+                'lcms2.2',
                 'crypto.1.0.0',
                 'ssl.1.0.0',
         ):

bypy/sources.json

@@ -153,6 +153,15 @@
         }
     },
 
+    {
+        "name": "lcms2",
+        "unix": {
+            "filename": "lcms2-2.11.tar.gz",
+            "hash": "sha256:478c9c3938d7a91b1171de4616f8b04308a8676d73eadc19505b7ace41327f28",
+            "urls": ["https://github.com/mm2/Little-CMS/archive/2.11/{filename}"]
+        }
+    },
+
     {
         "name": "graphite",
         "os": "linux",

docs/build.rst

@@ -18,6 +18,7 @@ Run-time dependencies:
     * harfbuzz >= 1.5.0
     * zlib
     * libpng
+    * liblcms2
     * freetype (not needed on macOS)
     * fontconfig (not needed on macOS)
     * libcanberra (not needed on macOS)

docs/changelog.rst

@@ -4,6 +4,13 @@ Changelog
 |kitty| is a feature full, cross-platform, *fast*, GPU based terminal emulator.
 To update |kitty|, :doc:`follow the instructions <binary>`.
 
+0.18.4 [2020-08-11]
+-------------------
+
+- Add support for displaying correct colors with non-sRGB PNG files (Adds a
+  dependency on liblcms2)
+
+
 0.18.3 [2020-08-11]
 -------------------
 

docs/graphics-protocol.rst

@@ -161,9 +161,10 @@ of transmitting paletted images.
 RGB and RGBA data
 ~~~~~~~~~~~~~~~~~~~
 
-In these formats the pixel data is stored directly as 3 or 4 bytes per pixel, respectively.
-When specifying images in this format, the image dimensions **must** be sent in the control data.
-For example::
+In these formats the pixel data is stored directly as 3 or 4 bytes per pixel,
+respectively. The colors in the data **must** be in the *sRGB color space*.  When
+specifying images in this format, the image dimensions **must** be sent in the
+control data. For example::
 
     <ESC>_Gf=24,s=10,v=20;<payload><ESC>\
 

kitty/png-reader.c

@@ -7,8 +7,10 @@
 
 #include "png-reader.h"
 #include "state.h"
+#include <lcms2.h>
 
 
+static cmsHPROFILE srgb_profile = NULL;
 struct fake_file { const uint8_t *buf; size_t sz, cur; };
 
 static void
@@ -64,13 +66,30 @@ inflate_png_inner(png_read_data *d, const uint8_t *buf, size_t bufsz) {
     bit_depth  = png_get_bit_depth(png, info);
     double image_gamma;
     int intent;
+    cmsHPROFILE input_profile = NULL;
+    cmsHTRANSFORM colorspace_transform = NULL;
     if (png_get_sRGB(png, info, &intent)) {
         // do nothing since we output sRGB
     } else if (png_get_gAMA(png, info, &image_gamma)) {
         if (image_gamma != 0 && fabs(image_gamma - 1.0/2.2) > 0.0001) png_set_gamma(png, 2.2, image_gamma);
     } else {
-        // do nothing since we don't know what gamma the source image is in
-        // TODO: handle images with color profiles
+        // Look for an embedded color profile
+        png_charp name;
+        int compression_type;
+        png_bytep profdata;
+        png_uint_32 proflen;
+        if (png_get_iCCP(png, info, &name, &compression_type, &profdata, &proflen) & PNG_INFO_iCCP) {
+            input_profile = cmsOpenProfileFromMem(profdata, proflen);
+            if (input_profile) {
+                if (!srgb_profile) {
+                    srgb_profile = cmsCreate_sRGBProfile();
+                    if (!srgb_profile) ABRT(ENOMEM, "Out of memory allocating sRGB colorspace profile");
+                }
+                colorspace_transform = cmsCreateTransform(
+                    input_profile, TYPE_RGBA_8, srgb_profile, TYPE_RGBA_8, INTENT_PERCEPTUAL, 0);
+
+            }
+        }
     }
 
     // Ensure we get RGBA data out of libpng
@@ -93,9 +112,17 @@ inflate_png_inner(png_read_data *d, const uint8_t *buf, size_t bufsz) {
     if (d->decompressed == NULL) ABRT(ENOMEM, "Out of memory allocating decompression buffer for PNG");
     d->row_pointers = malloc(d->height * sizeof(png_bytep));
     if (d->row_pointers == NULL) ABRT(ENOMEM, "Out of memory allocating row_pointers buffer for PNG");
-    for (int i = 0; i < d->height; i++) d->row_pointers[i] = d->decompressed + i * rowbytes;
+    for (int i = 0; i < d->height; i++) d->row_pointers[i] = d->decompressed + i * rowbytes * sizeof(png_byte);
     png_read_image(png, d->row_pointers);
 
+    if (colorspace_transform) {
+        for (int i = 0; i < d->height; i++) {
+            cmsDoTransform(colorspace_transform, d->row_pointers[i], d->row_pointers[i], d->width);
+        }
+        cmsDeleteTransform(colorspace_transform);
+    }
+    if (input_profile) cmsCloseProfile(input_profile);
+
     d->ok = true;
 err:
     if (png) png_destroy_read_struct(&png, info ? &info : NULL, NULL);
@@ -130,8 +157,20 @@ static PyMethodDef module_methods[] = {
     {NULL, NULL, 0, NULL}        /* Sentinel */
 };
 
+
+static void
+unload(void) {
+    if (srgb_profile) cmsCloseProfile(srgb_profile);
+    srgb_profile = NULL;
+}
+
 bool
 init_png_reader(PyObject *module) {
     if (PyModule_AddFunctions(module, module_methods) != 0) return false;
+    if (Py_AtExit(unload) != 0) {
+        PyErr_SetString(PyExc_RuntimeError, "Failed to register the PNG library at exit handler");
+        return false;
+    }
+
     return true;
 }

setup.py

@@ -329,6 +329,7 @@ def kitty_env() -> Env:
     cppflags.append('-DSECONDARY_VERSION={}'.format(version[1]))
     at_least_version('harfbuzz', 1, 5)
     cflags.extend(pkg_config('libpng', '--cflags-only-I'))
+    cflags.extend(pkg_config('lcms2', '--cflags-only-I'))
     if is_macos:
         font_libs = ['-framework', 'CoreText', '-framework', 'CoreGraphics']
         # Apple deprecated OpenGL in Mojave (10.14) silence the endless
@@ -342,7 +343,8 @@ def kitty_env() -> Env:
     pylib = get_python_flags(cflags)
     gl_libs = ['-framework', 'OpenGL'] if is_macos else pkg_config('gl', '--libs')
     libpng = pkg_config('libpng', '--libs')
-    ans.ldpaths += pylib + font_libs + gl_libs + libpng
+    lcms2 = pkg_config('lcms2', '--libs')
+    ans.ldpaths += pylib + font_libs + gl_libs + libpng + lcms2
     if is_macos:
         ans.ldpaths.extend('-framework Cocoa'.split())
     elif not is_openbsd: