+}
+
+// Propagate alpha information as far as we can in the graph.
+// Similar to propagate_gamma_and_color_space().
+void EffectChain::propagate_alpha()
+{
+ // We depend on going through the nodes in order.
+ sort_all_nodes_topologically();
+
+ for (unsigned i = 0; i < nodes.size(); ++i) {
+ Node *node = nodes[i];
+ if (node->disabled) {
+ continue;
+ }
+ assert(node->incoming_links.size() == node->effect->num_inputs());
+ if (node->incoming_links.size() == 0) {
+ assert(node->output_alpha_type != ALPHA_INVALID);
+ continue;
+ }
+
+ // The alpha multiplication/division effects are special cases.
+ if (node->effect->effect_type_id() == "AlphaMultiplicationEffect") {
+ assert(node->incoming_links.size() == 1);
+ assert(node->incoming_links[0]->output_alpha_type == ALPHA_POSTMULTIPLIED);
+ node->output_alpha_type = ALPHA_PREMULTIPLIED;
+ continue;
+ }
+ if (node->effect->effect_type_id() == "AlphaDivisionEffect") {
+ assert(node->incoming_links.size() == 1);
+ assert(node->incoming_links[0]->output_alpha_type == ALPHA_PREMULTIPLIED);
+ node->output_alpha_type = ALPHA_POSTMULTIPLIED;
+ continue;
+ }
+
+ // GammaCompressionEffect and GammaExpansionEffect are also a special case,
+ // because they are the only one that _need_ postmultiplied alpha.
+ if (node->effect->effect_type_id() == "GammaCompressionEffect" ||
+ node->effect->effect_type_id() == "GammaExpansionEffect") {
+ assert(node->incoming_links.size() == 1);
+ if (node->incoming_links[0]->output_alpha_type == ALPHA_BLANK) {
+ node->output_alpha_type = ALPHA_BLANK;
+ } else if (node->incoming_links[0]->output_alpha_type == ALPHA_POSTMULTIPLIED) {
+ node->output_alpha_type = ALPHA_POSTMULTIPLIED;
+ } else {
+ node->output_alpha_type = ALPHA_INVALID;
+ }
+ continue;
+ }
+
+ // Only inputs can have unconditional alpha output (OUTPUT_BLANK_ALPHA
+ // or OUTPUT_POSTMULTIPLIED_ALPHA), and they have already been
+ // taken care of above. Rationale: Even if you could imagine
+ // e.g. an effect that took in an image and set alpha=1.0
+ // unconditionally, it wouldn't make any sense to have it as
+ // e.g. OUTPUT_BLANK_ALPHA, since it wouldn't know whether it
+ // got its input pre- or postmultiplied, so it wouldn't know
+ // whether to divide away the old alpha or not.
+ Effect::AlphaHandling alpha_handling = node->effect->alpha_handling();
+ assert(alpha_handling == Effect::INPUT_AND_OUTPUT_PREMULTIPLIED_ALPHA ||
+ alpha_handling == Effect::INPUT_PREMULTIPLIED_ALPHA_KEEP_BLANK ||
+ alpha_handling == Effect::DONT_CARE_ALPHA_TYPE);
+
+ // If the node has multiple inputs, check that they are all valid and
+ // the same.
+ bool any_invalid = false;
+ bool any_premultiplied = false;
+ bool any_postmultiplied = false;
+
+ for (unsigned j = 0; j < node->incoming_links.size(); ++j) {
+ switch (node->incoming_links[j]->output_alpha_type) {
+ case ALPHA_INVALID:
+ any_invalid = true;
+ break;
+ case ALPHA_BLANK:
+ // Blank is good as both pre- and postmultiplied alpha,
+ // so just ignore it.
+ break;
+ case ALPHA_PREMULTIPLIED:
+ any_premultiplied = true;
+ break;
+ case ALPHA_POSTMULTIPLIED:
+ any_postmultiplied = true;
+ break;
+ default:
+ assert(false);
+ }
+ }
+
+ if (any_invalid) {
+ node->output_alpha_type = ALPHA_INVALID;
+ continue;
+ }
+
+ // Inputs must be of the same type.
+ if (any_premultiplied && any_postmultiplied) {
+ node->output_alpha_type = ALPHA_INVALID;
+ continue;
+ }
+
+ if (alpha_handling == Effect::INPUT_AND_OUTPUT_PREMULTIPLIED_ALPHA ||
+ alpha_handling == Effect::INPUT_PREMULTIPLIED_ALPHA_KEEP_BLANK) {
+ // If the effect has asked for premultiplied alpha, check that it has got it.
+ if (any_postmultiplied) {
+ node->output_alpha_type = ALPHA_INVALID;
+ } else if (!any_premultiplied &&
+ alpha_handling == Effect::INPUT_PREMULTIPLIED_ALPHA_KEEP_BLANK) {
+ // Blank input alpha, and the effect preserves blank alpha.
+ node->output_alpha_type = ALPHA_BLANK;
+ } else {
+ node->output_alpha_type = ALPHA_PREMULTIPLIED;
+ }
+ } else {
+ // OK, all inputs are the same, and this effect is not going
+ // to change it.
+ assert(alpha_handling == Effect::DONT_CARE_ALPHA_TYPE);
+ if (any_premultiplied) {
+ node->output_alpha_type = ALPHA_PREMULTIPLIED;
+ } else if (any_postmultiplied) {
+ node->output_alpha_type = ALPHA_POSTMULTIPLIED;
+ } else {
+ node->output_alpha_type = ALPHA_BLANK;
+ }
+ }
+ }
+}
+
+bool EffectChain::node_needs_colorspace_fix(Node *node)
+{
+ if (node->disabled) {
+ return false;
+ }
+ if (node->effect->num_inputs() == 0) {
+ return false;
+ }
+
+ // propagate_gamma_and_color_space() has already set our output
+ // to COLORSPACE_INVALID if the inputs differ, so we can rely on that.
+ if (node->output_color_space == COLORSPACE_INVALID) {
+ return true;
+ }
+ return (node->effect->needs_srgb_primaries() && node->output_color_space != COLORSPACE_sRGB);
+}
+
+// Fix up color spaces so that there are no COLORSPACE_INVALID nodes left in
+// the graph. Our strategy is not always optimal, but quite simple:
+// Find an effect that's as early as possible where the inputs are of
+// unacceptable colorspaces (that is, either different, or, if the effect only
+// wants sRGB, not sRGB.) Add appropriate conversions on all its inputs,
+// propagate the information anew, and repeat until there are no more such
+// effects.
+void EffectChain::fix_internal_color_spaces()
+{
+ unsigned colorspace_propagation_pass = 0;
+ bool found_any;
+ do {
+ found_any = false;
+ for (unsigned i = 0; i < nodes.size(); ++i) {
+ Node *node = nodes[i];
+ if (!node_needs_colorspace_fix(node)) {
+ continue;
+ }
+
+ // Go through each input that is not sRGB, and insert
+ // a colorspace conversion after it.
+ for (unsigned j = 0; j < node->incoming_links.size(); ++j) {
+ Node *input = node->incoming_links[j];
+ assert(input->output_color_space != COLORSPACE_INVALID);
+ if (input->output_color_space == COLORSPACE_sRGB) {
+ continue;
+ }
+ Node *conversion = add_node(new ColorspaceConversionEffect());
+ CHECK(conversion->effect->set_int("source_space", input->output_color_space));
+ CHECK(conversion->effect->set_int("destination_space", COLORSPACE_sRGB));
+ conversion->output_color_space = COLORSPACE_sRGB;
+ replace_sender(input, conversion);
+ connect_nodes(input, conversion);
+ }
+
+ // Re-sort topologically, and propagate the new information.
+ propagate_gamma_and_color_space();
+
+ found_any = true;
+ break;
+ }
+
+ char filename[256];
+ sprintf(filename, "step5-colorspacefix-iter%u.dot", ++colorspace_propagation_pass);
+ output_dot(filename);
+ assert(colorspace_propagation_pass < 100);
+ } while (found_any);
+
+ for (unsigned i = 0; i < nodes.size(); ++i) {
+ Node *node = nodes[i];
+ if (node->disabled) {
+ continue;
+ }
+ assert(node->output_color_space != COLORSPACE_INVALID);
+ }
+}
+
+bool EffectChain::node_needs_alpha_fix(Node *node)
+{
+ if (node->disabled) {
+ return false;
+ }
+
+ // propagate_alpha() has already set our output to ALPHA_INVALID if the
+ // inputs differ or we are otherwise in mismatch, so we can rely on that.
+ return (node->output_alpha_type == ALPHA_INVALID);
+}
+
+// Fix up alpha so that there are no ALPHA_INVALID nodes left in
+// the graph. Similar to fix_internal_color_spaces().
+void EffectChain::fix_internal_alpha(unsigned step)
+{
+ unsigned alpha_propagation_pass = 0;
+ bool found_any;
+ do {
+ found_any = false;
+ for (unsigned i = 0; i < nodes.size(); ++i) {
+ Node *node = nodes[i];
+ if (!node_needs_alpha_fix(node)) {
+ continue;
+ }
+
+ // If we need to fix up GammaExpansionEffect, then clearly something
+ // is wrong, since the combination of premultiplied alpha and nonlinear inputs
+ // is meaningless.
+ assert(node->effect->effect_type_id() != "GammaExpansionEffect");
+
+ AlphaType desired_type = ALPHA_PREMULTIPLIED;
+
+ // GammaCompressionEffect is special; it needs postmultiplied alpha.
+ if (node->effect->effect_type_id() == "GammaCompressionEffect") {
+ assert(node->incoming_links.size() == 1);
+ assert(node->incoming_links[0]->output_alpha_type == ALPHA_PREMULTIPLIED);
+ desired_type = ALPHA_POSTMULTIPLIED;
+ }
+
+ // Go through each input that is not premultiplied alpha, and insert
+ // a conversion before it.
+ for (unsigned j = 0; j < node->incoming_links.size(); ++j) {
+ Node *input = node->incoming_links[j];
+ assert(input->output_alpha_type != ALPHA_INVALID);
+ if (input->output_alpha_type == desired_type ||
+ input->output_alpha_type == ALPHA_BLANK) {
+ continue;
+ }
+ Node *conversion;
+ if (desired_type == ALPHA_PREMULTIPLIED) {
+ conversion = add_node(new AlphaMultiplicationEffect());
+ } else {
+ conversion = add_node(new AlphaDivisionEffect());
+ }
+ conversion->output_alpha_type = desired_type;
+ replace_sender(input, conversion);
+ connect_nodes(input, conversion);
+ }
+
+ // Re-sort topologically, and propagate the new information.
+ propagate_gamma_and_color_space();
+ propagate_alpha();
+
+ found_any = true;
+ break;
+ }
+
+ char filename[256];
+ sprintf(filename, "step%u-alphafix-iter%u.dot", step, ++alpha_propagation_pass);
+ output_dot(filename);
+ assert(alpha_propagation_pass < 100);
+ } while (found_any);
+
+ for (unsigned i = 0; i < nodes.size(); ++i) {
+ Node *node = nodes[i];
+ if (node->disabled) {
+ continue;
+ }
+ assert(node->output_alpha_type != ALPHA_INVALID);
+ }
+}
+
+// Make so that the output is in the desired color space.
+void EffectChain::fix_output_color_space()
+{
+ Node *output = find_output_node();
+ if (output->output_color_space != output_format.color_space) {
+ Node *conversion = add_node(new ColorspaceConversionEffect());
+ CHECK(conversion->effect->set_int("source_space", output->output_color_space));
+ CHECK(conversion->effect->set_int("destination_space", output_format.color_space));
+ conversion->output_color_space = output_format.color_space;
+ connect_nodes(output, conversion);
+ propagate_alpha();
+ propagate_gamma_and_color_space();
+ }
+}
+
+// Make so that the output is in the desired pre-/postmultiplication alpha state.
+void EffectChain::fix_output_alpha()
+{
+ Node *output = find_output_node();
+ assert(output->output_alpha_type != ALPHA_INVALID);
+ if (output->output_alpha_type == ALPHA_BLANK) {
+ // No alpha output, so we don't care.
+ return;
+ }
+ if (output->output_alpha_type == ALPHA_PREMULTIPLIED &&
+ output_alpha_format == OUTPUT_ALPHA_FORMAT_POSTMULTIPLIED) {
+ Node *conversion = add_node(new AlphaDivisionEffect());
+ connect_nodes(output, conversion);
+ propagate_alpha();
+ propagate_gamma_and_color_space();
+ }
+ if (output->output_alpha_type == ALPHA_POSTMULTIPLIED &&
+ output_alpha_format == OUTPUT_ALPHA_FORMAT_PREMULTIPLIED) {
+ Node *conversion = add_node(new AlphaMultiplicationEffect());
+ connect_nodes(output, conversion);
+ propagate_alpha();
+ propagate_gamma_and_color_space();
+ }
+}
+
+bool EffectChain::node_needs_gamma_fix(Node *node)
+{
+ if (node->disabled) {
+ return false;
+ }
+
+ // Small hack since the output is not an explicit node:
+ // If we are the last node and our output is in the wrong
+ // space compared to EffectChain's output, we need to fix it.
+ // This will only take us to linear, but fix_output_gamma()
+ // will come and take us to the desired output gamma
+ // if it is needed.
+ //
+ // This needs to be before everything else, since it could
+ // even apply to inputs (if they are the only effect).
+ if (node->outgoing_links.empty() &&
+ node->output_gamma_curve != output_format.gamma_curve &&
+ node->output_gamma_curve != GAMMA_LINEAR) {
+ return true;
+ }
+
+ if (node->effect->num_inputs() == 0) {
+ return false;
+ }
+
+ // propagate_gamma_and_color_space() has already set our output
+ // to GAMMA_INVALID if the inputs differ, so we can rely on that,
+ // except for GammaCompressionEffect.
+ if (node->output_gamma_curve == GAMMA_INVALID) {
+ return true;
+ }
+ if (node->effect->effect_type_id() == "GammaCompressionEffect") {
+ assert(node->incoming_links.size() == 1);
+ return node->incoming_links[0]->output_gamma_curve != GAMMA_LINEAR;
+ }
+
+ return (node->effect->needs_linear_light() && node->output_gamma_curve != GAMMA_LINEAR);
+}