1d33790dc0
It's a premultiplied image. This implies that we were misusing encodePNG in most cases, as we were passing premultiplied pixels which were then interpreted as unmultiplied. I changed encodePNG to accept premultipled pixels, and unpremultiply in the implementations.
122 lines
3.7 KiB
Plaintext
122 lines
3.7 KiB
Plaintext
#include <mbgl/util/image.hpp>
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#import <ImageIO/ImageIO.h>
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#if TARGET_OS_IPHONE
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#import <MobileCoreServices/MobileCoreServices.h>
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#else
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#import <CoreServices/CoreServices.h>
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#endif
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namespace mbgl {
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std::string encodePNG(const PremultipliedImage& src) {
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CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, src.data.get(), src.size(), NULL);
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if (!provider) {
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return "";
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}
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CGColorSpaceRef color_space = CGColorSpaceCreateDeviceRGB();
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if (!color_space) {
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CGDataProviderRelease(provider);
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return "";
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}
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CGImageRef image = CGImageCreate(src.width, src.height, 8, 32, 4 * src.width, color_space,
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kCGBitmapByteOrderDefault | kCGImageAlphaPremultipliedLast, provider, NULL, false,
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kCGRenderingIntentDefault);
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if (!image) {
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CGColorSpaceRelease(color_space);
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CGDataProviderRelease(provider);
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return "";
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}
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CFMutableDataRef data = CFDataCreateMutable(kCFAllocatorDefault, 0);
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if (!data) {
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CGImageRelease(image);
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CGColorSpaceRelease(color_space);
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CGDataProviderRelease(provider);
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return "";
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}
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CGImageDestinationRef image_destination = CGImageDestinationCreateWithData(data, kUTTypePNG, 1, NULL);
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if (!image_destination) {
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CFRelease(data);
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CGImageRelease(image);
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CGColorSpaceRelease(color_space);
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CGDataProviderRelease(provider);
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return "";
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}
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CGImageDestinationAddImage(image_destination, image, NULL);
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CGImageDestinationFinalize(image_destination);
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const std::string result {
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reinterpret_cast<const char *>(CFDataGetBytePtr(data)),
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static_cast<size_t>(CFDataGetLength(data))
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};
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CFRelease(image_destination);
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CFRelease(data);
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CGImageRelease(image);
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CGColorSpaceRelease(color_space);
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CGDataProviderRelease(provider);
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return result;
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}
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PremultipliedImage decodeImage(const std::string &source_data) {
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CFDataRef data = CFDataCreateWithBytesNoCopy(kCFAllocatorDefault, reinterpret_cast<const unsigned char *>(source_data.data()), source_data.size(), kCFAllocatorNull);
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if (!data) {
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throw std::runtime_error("CFDataCreateWithBytesNoCopy failed");
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}
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CGImageSourceRef image_source = CGImageSourceCreateWithData(data, NULL);
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if (!image_source) {
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CFRelease(data);
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throw std::runtime_error("CGImageSourceCreateWithData failed");
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}
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CGImageRef image = CGImageSourceCreateImageAtIndex(image_source, 0, NULL);
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if (!image) {
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CFRelease(image_source);
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CFRelease(data);
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throw std::runtime_error("CGImageSourceCreateImageAtIndex failed");
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}
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CGColorSpaceRef color_space = CGColorSpaceCreateDeviceRGB();
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if (!color_space) {
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CGImageRelease(image);
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CFRelease(image_source);
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CFRelease(data);
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throw std::runtime_error("CGColorSpaceCreateDeviceRGB failed");
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}
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PremultipliedImage result { CGImageGetWidth(image), CGImageGetHeight(image) };
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CGContextRef context = CGBitmapContextCreate(result.data.get(), result.width, result.height, 8, result.stride(),
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color_space, kCGImageAlphaPremultipliedLast);
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if (!context) {
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CGColorSpaceRelease(color_space);
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CGImageRelease(image);
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CFRelease(image_source);
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CFRelease(data);
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throw std::runtime_error("CGBitmapContextCreate failed");
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}
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CGContextSetBlendMode(context, kCGBlendModeCopy);
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CGRect rect = {{ 0, 0 }, { static_cast<CGFloat>(result.width), static_cast<CGFloat>(result.height) }};
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CGContextDrawImage(context, rect, image);
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CGContextRelease(context);
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CGColorSpaceRelease(color_space);
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CGImageRelease(image);
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CFRelease(image_source);
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CFRelease(data);
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return result;
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}
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}
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