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Photoshop cs5 by steve Johnson part 41

Tạo Channel mặt nạ từ Selections Tạo mặt nạ kênh từ đầu (bằng cách sử dụng bàn chải và các công cụ vẽ) là một tính năng hữu ích, và cho bạn khả năng để tạo ra một mặt nạ ở bất kỳ kích thước mong muốn hoặc hình dạng. Tuy nhiên, có những lúc nó sẽ được dễ dàng hơn để lần đầu tiên xác định các khu vực mà bạn muốn bảo vệ, và sau đó tạo ra các mặt nạ. | Creating Channel Masks from Selections Creating channel masks from scratch using brush and drawing tools is a useful feature and gives you the ability to create a mask in any desired size or shape. However there are times when it would be easier to first define the areas you want to protect and then create the mask. When you create a channel mask from an existing selection Photoshop uses the selected areas to create the mask. For example you have an image of a woman wearing a red dress and you want to change the color of the dress to green. The first step would be to select the red dress. Rather than create a new mask and paint out the area representing the dress it would be easier to first use a tool like the Magic Wand select the dress and then convert the selected area the dress into a channel mask. Once the mask is created you could finetune the mask using Photoshop s painting tools and then change the dress color. Whether you create a mask from scratch or choose to create one through a predefined selection depends on the image and what you re trying to accomplish. Create Channel Masks from Selections Open a document. Create a selection using any of Photoshop s traditional selection tools. Select the Channels panel. Click the Save Selection As Channel button. Photoshop creates a new channel mask based on the selected areas of the document. The selection is converted into an Alpha mask. Chapter 10 Creating Masks 255 Making Channel Masks from Native Color Channels Creating a channel mask from a native color channel takes a few steps however if you re successful the effort spent making the selection is well worth it. The trick to creating a mask with a native color channel is to use the shifts of gray in one specific color channel to create the black and white areas characteristic of a typical channel mask. For example you have an image of a model and you want to remove the model from the background. Unfortunately that requires selecting around the model s hair a