About

Solid-color images serve as calibration targets, placeholder assets, CSS fallback backgrounds, and test fixtures for image pipelines. Getting the output wrong - incorrect color space mapping, unintended compression artifacts, or off-by-one pixel dimensions - propagates errors downstream into design mockups, automated tests, and print workflows. This tool generates a real JPEG binary using the browser Canvas API. You select a color via hex value (sRGB gamut), define W × H pixel dimensions up to 8192 × 8192, and control JPEG compression quality from 1% to 100%. The output is a standards-compliant JFIF file with no metadata bloat. Note: JPEG is lossy - even a solid color at quality < 100% will exhibit minor block artifacts near edges due to 8×8 DCT quantization.

Formulas

The generator fills a Canvas element with a uniform color then exports it as a JPEG blob. The core operation is trivial but the output file size depends on JPEG compression behavior.

fileSize ≈ f(W, H, Q)

Where W = width in pixels, H = height in pixels, Q = JPEG quality factor (0.01 to 1.0). For a solid color image, JPEG compression is highly efficient because all 8×8 DCT blocks are identical. Uncompressed bitmap size is:

rawSize = W × H × 3 bytes

The factor 3 accounts for 8-bit R, G, B channels. JPEG output for uniform content is typically < 1% of raw size due to DCT coefficient redundancy. The actual file size is computed from the generated Blob object: blob.size returns the exact byte count.

Reference Data

Preset	Hex Code	RGB	Common Use
Pure White	#FFFFFF	255, 255, 255	Backgrounds, product photography
Pure Black	#000000	0, 0, 0	OLED wallpapers, letterboxing
Signal Red	#FF0000	255, 0, 0	Monitor dead-pixel test
Signal Green	#00FF00	0, 255, 0	Chroma key, dead-pixel test
Signal Blue	#0000FF	0, 0, 255	Color channel isolation
18% Gray	#737373	115, 115, 115	Photographic exposure calibration
50% Gray	#808080	128, 128, 128	Neutral overlay blending base
Transparent Pink	#FF00FF	255, 0, 255	Missing texture indicator (gamedev)
Safety Orange	#FF6600	255, 102, 0	Warning signage, high visibility
Cornflower Blue	#6495ED	100, 149, 237	Default Direct3D clear color
Web Yellow	#FFFF00	255, 255, 0	Highlight, dead-pixel test
Cyan	#00FFFF	0, 255, 255	Print CMYK test, subtractive primary
Instagram Gradient Start	#833AB4	131, 58, 180	Social media placeholder backgrounds
Slack Aubergine	#4A154B	74, 21, 75	Brand color matching
Material Teal	#009688	0, 150, 136	Material Design placeholder

Frequently Asked Questions

JPEG uses 8×8 pixel block DCT (Discrete Cosine Transform) compression. At quality values below approximately 50%, the quantization matrix aggressively rounds DCT coefficients, introducing visible block-boundary artifacts even in uniform-color images. For artifact-free solid colors, keep quality at 95% or above. At 100% quality, most browsers apply minimal quantization that preserves the exact color for solid fills.

Most modern browsers support canvas dimensions up to 8192×8192 pixels (67 megapixels). Some mobile browsers cap at 4096×4096. This tool clamps at 8192px per side. If the canvas fails to allocate, the browser silently returns a blank image. For extremely large outputs (e.g., print at 300 DPI for a poster), generate at 8192px and upscale in a vector editor.

No. The Canvas API toBlob method produces a minimal JFIF-compliant JPEG with no EXIF, IPTC, or XMP metadata. The file contains only the JFIF header, quantization tables, Huffman tables, and scan data. If you need metadata (copyright, DPI tags), add it post-export with an EXIF editor tool.

The HTML color input provides sRGB hex values. The Canvas 2D context operates in sRGB by default. JPEG internally converts to YCbCr color space during encoding. For a solid color, the Y (luminance), Cb, and Cr (chrominance) channels each contain a single constant value across all 8×8 blocks, making compression extremely efficient. The decoded JPEG will visually match the input hex in any sRGB-aware viewer.

JPEG compression exploits spatial redundancy via the DCT. In a solid-color image, every 8×8 block has identical pixel values. The DCT of a constant block yields only a single non-zero DC coefficient (all AC coefficients are zero). The Huffman/arithmetic entropy coder then compresses these repeated DC values extremely efficiently. A 4000×4000 solid-color JPEG at quality 90% typically occupies only 5-15 KB.

No. JPEG does not support an alpha (transparency) channel. The format encodes only RGB data. If you need transparency, use PNG or WebP format instead. This tool is specifically designed for opaque solid-color JPEG output.