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�U�L��地图�l�制引擎从Qt切换到Cairo

攑ֱ�阿狗 — Sat, 31 Aug 2013 07:39:00 GMT

�׃��最�q�也是比较有旉��Q�想着��Windows版本的地囄��制引擎移植到Linux�?br />地图Render部分采用的是Qt�Q�所以过�E�非帔R��利，用Eclipse+CDT重徏工程�Q�略微几个小改动便完成了�U�L��?br />但之后发��C��Qt带来的问题了�Q�地囄��制引擎支持�ƈ发处理多个绘制请求，不同的绘制请求将在不同的�U�程Thread中被执行�Q�多�U�程的情况便出现了问题，提示QPixmap不能在非UI�U�程被构造，如果��构造，便出��C��内存数据讉K��q�例的异帔R��误，�q�程直接coredump�Q�这个问题困��C��一些时��_(d��)��
之后改了改代码，��数据处理和�l�制代码隔离开�Q�线�E�thread中进行数据加载、分析、计��，�l�制代码采用Qt的signal/slot机制完成�Q�就是工作线�E�处理好数据之后通过emit signal��绘制请求发送给ui�ȝ��E�的slot处理函数。这�U�实现方法的问题在于�l�制工作都将被串行执行，性能下降�?br />几年前在�U�L��libsvg到wince旉��用过cairo( cairographices.org) ,有点使用�l�验�Q�且cairo是gnome的标准图形库�Q�性能应该不错�Q�所以直接改为cairo�?br />cairomm是cairo的c++包装�Q�编译还需sig++�Q�cairo的api�q�是��Z��富的�Q�字体，反走��P��矩阵... 操作也是相当��?nbsp;
很快�U�L��完成�Q�运行效果还是比较满意，现在正考虑地图引擎�U�L��到ios讑֤��Q�目前需要琢��cairomm�Q�sig++�Q�pixmap之类的东西如何移植问�?或者直接采用ios的Fundation的绘图api)

攑ֱ�阿狗 2013-08-31 15:39 发表评论

PPM(portable pixel map)

攑ֱ�阿狗 — Tue, 24 Jun 2008 13:11:00 GMT

reference: http://netpbm.sourceforge.net/doc/ppm.html

Each PPM image consists of the following:

A "magic number" for identifying the file type. A ppm image's magic number is the two characters "P6".
Whitespace (blanks, TABs, CRs, LFs).
A width, formatted as ASCII characters in decimal.
Whitespace.
A height, again in ASCII decimal.
Whitespace.
The maximum color value (Maxval), again in ASCII decimal. Must be less than 65536 and more than zero.
A single whitespace character (usually a newline).
A raster of Height rows, in order from top to bottom. Each row consists of Width pixels, in order from left to right. Each pixel is a triplet of red, green, and blue samples, in that order. Each sample is represented in pure binary by either 1 or 2 bytes. If the Maxval is less than 256, it is 1 byte. Otherwise, it is 2 bytes. The most significant byte is first.
A row of an image is horizontal. A column is vertical. The pixels in the image are square and contiguous.
In the raster, the sample values are "nonlinear." They are proportional to the intensity of the ITU-R Recommendation BT.709 red, green, and blue in the pixel, adjusted by the BT.709 gamma transfer function. (That transfer function specifies a gamma number of 2.2 and has a linear section for small intensities). A value of Maxval for all three samples represents CIE D65 white and the most intense color in the color universe of which the image is part (the color universe is all the colors in all images to which this image might be compared).
ITU-R Recommendation BT.709 is a renaming of the former CCIR Recommendation 709. When CCIR was absorbed into its parent organization, the ITU, ca. 2000, the standard was renamed. This document once referred to the standard as CIE Rec. 709, but it isn't clear now that CIE ever sponsored such a standard.

Note that another popular color space is the newer sRGB. A common variation on PPM is to subsitute this color space for the one specified.
Note that a common variation on the PPM format is to have the sample values be "linear," i.e. as specified above except without the gamma adjustment. pnmgamma takes such a PPM variant as input and produces a true PPM as output.
Strings starting with "#" may be comments, the same as with PBM.

攑ֱ�阿狗 2008-06-24 21:11 发表评论

攑ֱ�阿狗 — Thu, 08 May 2008 12:07:00 GMT

Image Decoder:
libpng,libjpeg,libtiff,

Image�?
cimg, devil,python-pil,agg,cximage,gdk-pixbuf,wxImage(wxWidget)�Q�magic-image

cimg: 采用template技术，整个库就一个cimg.h�Q��用�v来确实方便其内在功能��实强大,只是��单应用了一�?br>pil: 用python写过4国军旗的游戏,采用的就是这个image�?br>agg: 采用template技术，几乎�늛��?d image操作的所有功能，也是��p��合�Q��用�v来非常灵�z?br>cximage: 做导航设备的囄��览软�g旉��用image 库，基本�q�是比较好用
gdk-pixbuf: gdk/gtk标准的image 库，gnome的大量��Y件均采用其库。移�?librsvg时��用过
wxImage: 依赖 wxWidget库，�c�M�� Qt�?QtImage�c?br>

攑ֱ�阿狗 2008-05-08 20:07 发表评论